PDF

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{{FormatInfo
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|[[File Formats]]
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|formattype=electronic
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| >
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|subcat=Document
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|[[Electronic File Formats]]
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|extensions={{ext|pdf}}
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| >
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|mimetypes={{mimetype|application/pdf}}
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|[[Documents]]
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|locfdd={{LoCFDD|fdd000030}}, others
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| >
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|pronom={{PRONOM|fmt/276}}, others
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|PDF
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|wikidata={{wikidata|Q42332}}
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}}
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'''Portable Document Format''' ('''PDF''') is a document file format originally from Adobe, based on [[PostScript]]. It has many subsets.
 +
 
 +
As well as the 'full function' ISO 32000-1:2008 (or PDF 1.7), there are also PDF/X, PDF/A, PDF/E, PDF/VT and PDF/UA, all of which are ISO specifications.
 +
 
 +
PDF profiles (formalized subsets) include the following:
 +
 
 +
* PDF/A (optimized for preservation)
 +
** PDF/A-1 (ISO 19005-1:2005)
 +
** PDF/A-2 (ISO 19005-2:2011)
 +
** PDF/A-3 (ISO 19005-3:2012) (extends PDF/A-2 by allowing embedded files of any type)
 +
** PDF/A-4 (ISO 19005-4:2020)
 +
* PDF/E (ISO 24517-1:2008) (for engineering workflows)
 +
* PDF/UA (ISO 14289-1) (making documents accessible through assistive technologies)
 +
* PDF/VT (ISO 16612-2) (support for variable document printing)
 +
* PDF/X (support for prepress graphics exchange)
 +
** PDF/X-1 (ISO 15930-1:2001)
 +
** PDF/X-1a (ISO 15930-4:2003)
 +
** PDF/X-2 (ISO 15930-5:2003)
 +
** PDF/X-3 (ISO 15930-6:2003)
 +
* Tagged PDF
 +
Some scanner documentation references an apparently fictitious "PDF/L" profile (see Gary McGath's [https://madfileformatscience.garymcgath.com/2018/03/21/pdf-l/ "PDF/L?"]).
 +
 
 +
A PDF 2.0 spec (ISO 32000-2) was published in 2017-07, with some new features as well as clarification of conformance with existing features.
 +
 
 +
A PDF/raster draft spec was issued in 2017 as a subset of PDF files containing raster images of scanned documents.
 +
 
 +
== Identifiers ==
 +
{| class="wikitable"
 +
! Format
 +
! PRONOM
 +
! LoCFDD
 +
|-
 +
|PDF ||  || {{LoCFDD|fdd000030}}
 +
|-
 +
|PDF 1.0 || {{PRONOM|fmt/14}} ||rowspan="4"| {{LoCFDD|fdd000316}}
 +
|-
 +
|PDF 1.1 || {{PRONOM|fmt/15}}
 +
|-
 +
|PDF 1.2 || {{PRONOM|fmt/16}}
 +
|-
 +
|PDF 1.3 || {{PRONOM|fmt/17}}
 +
|-
 +
|PDF 1.4 || {{PRONOM|fmt/18}} || {{LoCFDD|fdd000122}}
 +
|-
 +
|PDF 1.5 || {{PRONOM|fmt/19}} || {{LoCFDD|fdd000123}}
 +
|-
 +
|PDF 1.6 || {{PRONOM|fmt/20}} || {{LoCFDD|fdd000276}}
 +
|-
 +
|PDF 1.7 || {{PRONOM|fmt/276}} || {{LoCFDD|fdd000277}}
 +
|-
 +
|PDF 1.7, Ext. 3 ||  || {{LoCFDD|fdd000313}}
 +
|-
 +
|PDF 2.0 || {{PRONOM|fmt/1129}}
 +
|-
 +
|PDF/A    ||  || {{LoCFDD|fdd000318}}
 +
|-
 +
|PDF/A-1  ||  || {{LoCFDD|fdd000125}}
 +
|-
 +
|PDF/A-1a || {{PRONOM|fmt/95}} || {{LoCFDD|fdd000251}}
 +
|-
 +
|PDF/A-1b || {{PRONOM|fmt/354}} || {{LoCFDD|fdd000252}}
 +
|-
 +
|PDF/A-2  ||  || {{LoCFDD|fdd000319}}
 +
|-
 +
|PDF/A-2a || {{PRONOM|fmt/476}} || {{LoCFDD|fdd000320}}
 +
|-
 +
|PDF/A-2b || {{PRONOM|fmt/477}} || {{LoCFDD|fdd000322}}
 +
|-
 +
|PDF/A-2u || {{PRONOM|fmt/478}} || {{LoCFDD|fdd000321}}
 +
|-
 +
|PDF/A-3a || {{PRONOM|fmt/479}} ||rowspan="3"| {{LoCFDD|fdd000360}}
 +
|-
 +
|PDF/A-3b || {{PRONOM|fmt/480}}
 +
|-
 +
|PDF/A-3u || {{PRONOM|fmt/481}}
 +
|-
 +
|PDF/A-4 || || {{LoCFDD|fdd000532}}
 +
|-
 +
|PDF/X-1  || {{PRONOM|fmt/144}}, {{PRONOM|fmt/145}} ||rowspan="9"| {{LoCFDD|fdd000124}}
 +
|-
 +
|PDF/X-1a || {{PRONOM|fmt/157}}, {{PRONOM|fmt/146}}
 +
|-
 +
|PDF/X-2  || {{PRONOM|fmt/147}}
 +
|-
 +
|PDF/X-3  || {{PRONOM|fmt/158}}, {{PRONOM|fmt/148}}
 +
|-
 +
|PDF/X-4  || {{PRONOM|fmt/488}}
 +
|-
 +
|PDF/X-4p  || {{PRONOM|fmt/489}}
 +
|-
 +
|PDF/X-5g  || {{PRONOM|fmt/490}}
 +
|-
 +
|PDF/X-5pg || {{PRONOM|fmt/491}}
 +
|-
 +
|PDF/X-5n  || {{PRONOM|fmt/492}}
 +
|-
 +
|PDF/UA-1 ||  || {{LoCFDD|fdd000350}}
 +
|-
 +
|PDF/E-1  || {{PRONOM|fmt/493}}
 +
|-
 +
|PDF, Geospatial ||  || {{LoCFDD|fdd000315}}
 +
|-
 +
|GeoPDF 2.2 ||  || {{LoCFDD|fdd000312}}
 +
|-
 +
|PDF Portfolio  || {{PRONOM|fmt/1451}}
 
|}
 
|}
  
−
'''PDF''', portable document format, based on [[PS|PostScript]] and originally from Adobe, has many subsets.  
+
== Identification ==
 +
The majority of PDF files can be identified by a fixed header e.g. "%PDF-1.4", however, older documents have a number of variations.
 +
* Some can start with "%!PS-Adobe-N.n PDF-M.m" instead, as described [http://blog.didierstevens.com/2010/01/21/quickpost-pdf-header-ps-adobe-n-n-pdf-m-m/ here].
 +
* Since PDF 1.7, the major and minor version numbers have been fixed. i.e. the public version from Adobe after 1.7 was "1.7 Adobe Extension Level 3".
 +
* For the PDF/A families of formats, their conformance is declared via an embedded ([[XMP]]) metadata fragment.
 +
* Some older files from Mac OS may be wrapped up in the [[AppleSingle]]/[[AppleDouble]] formats. This is a general issue, so should perhaps be documented elsewhere. For more information, see:
 +
** http://en.wikipedia.org/wiki/AppleSingle_and_AppleDouble_formats
 +
** http://tools.ietf.org/rfc/rfc1740.txt
  
−
As well as the 'full function' ISO 32000-1:2008 (or PDF 1.7) there is also PDF/X, PDF/A, PDF/E, PDF/VT and PDF/UA all of which are ISO specifications.
+
== Compression ==
 +
Images in PDF documents may use the following compression schemes:
 +
* [[LZW]]
 +
* Flate ([[zlib]])
 +
* [[Run-length encoding|RunLength]]
 +
* CCITTFax ([[CCITT Group 3]] and [[CCITT Group 4]])
 +
* [[JBIG2]]
 +
* DCT ([[JPEG]])
 +
* [[JPX]] (part of the [[JPEG 2000]] standard)
  
−
== References ==
+
== Digital Rights Management & Encryption ==
 +
PDF has two types of 'encryption' - it uses an 'user' password to limit the ability to open the document, and a 'creator' password to limit other rights, like printing, copying, etc. The former case, where a password is required to open the file, is the main preservation concern, as our users will not be able to open a PDF encrypted in this way (unless the password can be cracked, which may be problematic both technically and legally). However, the latter case causes problems, because the PDF is encrypted here too, but with a special known user password of "" (an empty string, which is not the same as no password). So, the document is encrypted in both cases, and you can only tell which is which by attempting to decrypt the PDF using the special default password "". Some PDF analysis tools (notably [[JHOVE]]) do not implement the relevant decryption workflow, and so cannot distinguish between the two types of encryption.
 +
 
 +
An example of the decryption test workflow can be found here: https://gist.github.com/anjackson/5237071
 +
 
 +
Some of the most locked-up PDFs anywhere can be found at the [http://ibr.ansi.org/ ANSI IBR Standards Portal], which has made certain standards documents that are incorporated into legislation available for browsing, but only through a convoluted procedure involving downloading a special plug-in and filling out a registration form that must be re-filled-out in every browsing session.
 +
 
 +
A "Protected PDF" (PPDF) format is [http://www.eweek.com/mobile/microsoft-enterprise-mobility-suite-cozies-up-to-office.html reportedly] used by Microsoft's Azure Rights Management Service for sharing files securely within a workgroup.
 +
 
 +
== Document redaction ==
 +
 
 +
Occasionally the attempts of technically-inept users to obscure content in PDF files get in the news. People have sometimes had the mistaken impression that if a section of text is overlayed with a solid-black shape, or set to white-on-white text, or some such thing, before the publicly distributed document is sent out, that would make the redacted sections unavailable; this is not true, as it is in fact easy to find text that has been obscured in such manners, often as simple as dragging a mouse over it to highlight it. This happened in a [http://www.sun-sentinel.com/opinion/fl-op-editorial-judge-elizabeth-scherer-20180823-story.html 2018 Florida case] connected with the school shooting there, where some parts of the school district's report about the shooter were badly redacted and disclosed by a local newspaper, leading to a judge threatening punishment of the paper and prior restraint of future publications of theirs because of this "hacking", raising all sorts of legal and constitutional issues.
 +
 
 +
== Web linking ==
 +
 
 +
When linked on the [[Web]], specific pages of a PDF can be referenced by appending <code>#page=N</code> (where N is the desired page number) as a fragment identifier at the end of the [[URL]]. This is a little-known fact.
 +
 
 +
== Specifications ==
 +
* [https://web.archive.org/web/20150228065316/http://acroeng.adobe.com/wp/?page_id=321 Adobe PDF References (archived)]  Contains links to every version of the PDF Reference published by Adobe (starting with PDF 1.0) as well as associated errata, addenda and tech notes.
 +
* [https://pdfa.org/resource/pdf-specification-archive/ PDF Specification Archive]
 +
* Other sources of the above documents:
 +
** [http://www.adobe.com/devnet/pdf/pdf_reference.html PDF Reference and Adobe Extensions to the PDF Specification] Adobe page linking to specification for PDF 1.7 (equivalent to ISO 32000-1:2008) and two Adobe extensions that are expected to be incorporated into ISO 32000-2. These extensions include support for geospatial features and for 3-D content using [[U3D]] and [[Adobe PRC|PRC]] formats.
 +
** [http://www.adobe.com/devnet/pdf/pdf_reference_archive.html Adobe PDF Reference Archives.] Archive of specifications for earlier Adobe versions of PDF, starting with Version 1.3.
 +
* [https://www.iso.org/standard/51502.html ISO 32000-1:2008]: PDF 1.7 (not free to download)
 +
* [https://www.iso.org/standard/63534.html ISO 32000-2:2017]: PDF 2.0 (not free to download)
 +
* [https://pdfraster.org/wp-content/uploads/2017/06/PDFraster10_June-2017.pdf Draft PDF/raster spec 1.0]
 +
 
 +
== Software ==
 +
* [http://get.adobe.com/reader/ Adobe Reader] views PDF files, either as a standalone program or a browser plugin.
 +
* [http://www.mozilla.org/en-US/products/download.html?product=firefox-19.0&os=win&lang=en-US Firefox 19.0] includes a built-in PDF reader.
 +
* [http://source.mozillaopennews.org/en-US/articles/introducing-tabula/ Tabula: convert tabular data in PDFs to CSV]
 +
* [http://www.mpdf1.com/mpdf/index.php mPDF: convert HTML to PDF]
 +
* [https://mupdf.com/ MuPDF PDF viewer and command line mutool for manipulating PDF]
 +
* [https://eternal-todo.com/tools/peepdf-pdf-analysis-tool peepdf: powerful Python tool to analyze and explore PDFs]
 +
* [http://en.pdf24.org/ PDF24 creator]
 +
* [http://pdfbox.apache.org/ Apache PDFBox] is an open-source PDF library that includes a PDF/A validator
 +
* [https://pdfium.googlesource.com/pdfium/ pdfium: Open source PDF rendering engine]
 +
* [http://textract.readthedocs.org/en/latest/ Textract: extract text from various document formats including PDF]
 +
* [https://github.com/pramodhkp/pdf2svg/ pdf2svg (in JavaScript)]
 +
* [https://euske.github.io/pdfminer/programming.html Programming with PDFMiner]
 +
* [https://github.com/friesey/preservation-tools/releases/tag/v0.1_alpha_PDFBox_Statistics PDFBox PDF/A Validator]
 +
* [https://pypi.python.org/pypi/PyPDF2/1.24 PyPDF2]
 +
* [https://github.com/sumatrapdfreader Sumatra PDF Reader]
 +
* [https://chrome.google.com/webstore/detail/pdf-viewer/oemmndcbldboiebfnladdacbdfmadadm?hl=en PDF viewer for Chrome]
 +
* [http://verapdf.org/software/ veraPDF library (PDF validator)]
 +
* [http://www.metachris.com/pdfx/ PDFx - Extract metadata and URLs from PDFs, and download all referenced PDFs]
 +
* [https://github.com/ANSSI-FR/caradoc Caradoc: PDF parser and validator]
 +
* [https://github.com/uds-datalab/PDBF PBDF: Create documents that are simultaneously valid PDF, HTML, and VirtualBox OVA.]
 +
* [https://blog.didierstevens.com/programs/pdf-tools/ PDF Tools]
 +
* [https://www.tracker-software.com/product/pdf-xchange-viewer PDF-XChange Viewer]
 +
* [https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/ The PDF Toolkit PDFTK]
 +
* [https://www.ghostscript.com/doc/Readme.htm Ghostscript (can both read and write PDF)]
 +
 
 +
== Online utilities ==
 +
* [http://www.pdf4kindle.com/ PDF to Kindle converter]
 +
* [https://pdftables.com/ PDF to Excel (and some other formats)]
 +
* [https://www.ilovepdf.com/ I Love PDF: miscellaneous utilities]
 +
 
 +
== Sample files ==
 +
* [https://github.com/openplanets/format-corpus/tree/master/pdfCabinetOfHorrors PDF Cabinet of Horrors] - sample PDF files in corrupted or otherwise problematic formats
 +
* [http://acroeng.adobe.com/wp/?page_id=10 Adobe PDF Test Suites] - various PDF test suites on Adobe Acrobat Engineering site
 +
* [http://craphound.com/homeland/Cory_Doctorow_-_Homeland.pdf Homeland by Cory Doctorow]
 +
* [https://www.dan.info/sampledata/msword/testing.pdf Sample document saved from Windows Word 2007]
 +
* [https://github.com/corkami/pocs/blob/master/pdf/quine.pdf Quine PDF; contains its own TeX source]
 +
* [https://www.alchemistowl.org/pocorgtfo/pocorgtfo08.pdf Newsletter designed to work as PDF, ZIP, or shell script]
 +
* [https://github.com/veraPDF/veraPDF-corpus veraPDF corpus]
 +
* [https://github.com/osnr/horrifying-pdf-experiments Horrifying PDF Experiments]
 +
* [https://github.com/mozilla/pdf.js/tree/master/test/pdfs Test PDFs used by Mozilla PDF Reader]
 +
* [https://github.com/pdf-association/pdf20examples PDF 2.0 example files by the PDF Association]
 +
* {{DexvertSamples|document/pdf}}
 +
 
 +
== See also ==
 +
* [[Ascii85]]
 +
* [[FDF]]
 +
* [[KFP]] Preflight Profile
 +
* [[PostScript]]
 +
* [[WWF]]
 +
* [[XFDF]]
 +
 
 +
== Links ==
 +
 
 +
=== Format info ===
 
* [http://en.wikipedia.org/wiki/Portable_Document_Format Portable Document Format (Wikipedia)]
 
* [http://en.wikipedia.org/wiki/Portable_Document_Format Portable Document Format (Wikipedia)]
 +
* [{{ForensicsWikiURL|pdf}} Forensics Wiki: PDF]
 +
*[http://acroeng.adobe.com/wp/ Adobe Acrobat Engineering site] - Dedicated Adobe site with lots of technical information, including a history of PDF and Acrobat, conforming viewers and test files.
 +
* [http://www.pdfa.org/2013/04/pdfa-in-a-nutshell-2_0/ PDF/A in a Nutshell 2.0 – online edition]
 +
* [http://www.infinitepartitions.com/cgi-bin/showarticle.cgi?article=art019 Inside the PDF File Format]
 +
* [http://imgur.com/a/PbN8H#7 PDF101 an Adobe document walkthrough]
 +
 +
=== Validation ===
 +
* [http://vimeopro.com/pdfassociation/technical-conference-europe-2013/video/68945979 PDF Validation: Dream or Yawn?] - Presentation on possibilities of an open-source PDF validator
 +
* [http://www.docdroid.net/ciex/5103a198-1.pdf.html The pitfalls of protocol design: Attempting to write a formally verified PDF parser]
 +
* [https://fileformats.wordpress.com/2015/04/22/verapdf/ New open-source file validation project]
 +
 +
=== Jailbreaking ===
 +
* [http://scholrev.org/hackathon/ Jailbreaking the PDF hackathon]
 +
* [http://blogs.ch.cam.ac.uk/pmr/2013/05/28/jailbreaking-the-pdf-a-wonderful-hackathon-and-a-community-leap-forward-for-freedom-1/ Jailbreaking the PDF (discussion)]
 +
* [http://blogs.ch.cam.ac.uk/pmr/2013/05/28/jailbreaking-the-pdf-2-technical-aspects-glyph-processing/ Jailbreaking the PDF (technical aspects: glyph processing)]
 +
* [http://blog.didierstevens.com/2015/04/15/pdf-password-cracking-with-john-the-ripper/ PDF Password Cracking With John The Ripper]
 +
 +
=== Commentary ===
 +
* [http://www.portico.org/digital-preservation/wp-content/uploads/2012/11/TheNetworkIsTheFormat.pdf The Network is the Format: PDF and the Long-term Use of Digital Content] Article by Sheila Morrissey of ITHAKA on the challenges of preserving PDF files based on experience.  She illustrates the challenge of defining a "sufficient sub-graph of the network of information about a digital object, for effective future use."
 +
* [http://blogs.loc.gov/digitalpreservation/2014/06/the-pdfs-place-in-a-history-of-paper-knowledge-an-interview-with-lisa-gitelman/ The PDF’s Place in a History of Paper Knowledge: An Interview with Lisa Gitelman]
 +
*[http://wiki.opf-labs.org/display/TR/Portable+Document+Format Portable Document Format on OPF File Format Risk Registry] - Lists various long-term accessibility issues in PDF and how to detect them using Apache Preflight.
 +
* [http://www.openplanetsfoundation.org/system/files/PDFInventoryPreservationRisks_0_2_0.pdf  Adobe Portable Document Format - Inventory of long-term preservation risks] - Report by KB/ National Library of the Netherlands.
 +
* [http://fileformats.wordpress.com/2014/06/13/abuses-pdf/ The uses and abuses of PDF]
 +
* [http://duff-johnson.com/2014/04/07/apples-preview-still-not-safe-for-work/ Apple’s Preview: Still not safe for work]
 +
* [http://www.niso.org/publications/isq/2013/v25no3/moore/ Preserving the Grey Literature Explosion: PDF/A and the Digital Archive]
 +
* [http://www.pdfa.org/2014/12/ensuring-long-term-access-pdf-validation-with-jhove/ Ensuring long-term access: PDF validation with JHOVE?]
 +
* [http://www.theguardian.com/higher-education-network/2015/feb/11/researchers-its-time-to-ditch-the-pdf Researchers: it's time to ditch the PDF]
 +
* [http://wiki.dpconline.org/images/5/51/PDF_Assessment_v1.2_external.pdf PDF Format Preservation Assessment (British Library)]
 +
* [http://www.pdfa.org/2015/06/what-will-pdf-2-0-bring/ What will PDF 2.0 bring?]
 +
* [http://www.digitalpreservation.gov/ndsa/working_groups/documents/NDSA_PDF_A3_report_final022014.pdf?loclr=blogsig The Benefits and Risks of the PDF/A-3 file format for archival institutions]
 +
* [https://nicolastreeten.wordpress.com/2015/09/19/becoming-of-age-pdf/ Becoming of Age: PDF (comic)]
 +
* [http://www.pdfa.org/2016/06/what-does-support-pdf-really-mean/ What does "support PDF" really mean?]
 +
* [http://openpreservation.org/blog/2016/12/09/pdfa-as-a-preferred-sustainable-format-for-spreadsheets/ PDF/A as a preferred, sustainable format for spreadsheets?]
 +
* [https://www.filingdb.com/pdf-text-extraction What's so hard about PDF text extraction?]
 +
* [https://www.pdfa.org/perfecting-pdf-lexical-analysis/ Perfecting PDF lexical analysis]
 +
 +
=== Miscellaneous ===
 +
* [http://www.pdfa.org/ PDF/A Competence Center]
 +
* [http://web.archive.org/web/20130515073645/http://libraries.stackexchange.com/questions/964/what-preservation-risks-are-associated-with-the-pdf-file-format What preservation risks are associated with the PDF file format?] - Q&A thread  from Libraries and Information Sciences Stack Exchange (archived)
 +
* [http://labs.appligent.com/files/2013/03/recognizing_malformed_pdf_f.pdf Recognizing Corrupt and Malformed PDF Files]
 +
* [https://github.com/davetaz/mh370-data Flight MH370 data was released as a PDF, but somebody extracted it to CSV to make it more useful for data analysis.]
 +
* [https://pdf.yt/ PDFy - free host for publicly viewable PDFs, backed up automatically to Internet Archive]
 +
* [http://www.washingtonpost.com/blogs/the-switch/wp/2014/08/05/uk-judge-says-freedom-of-information-means-choice-of-digital-file-format/ UK judge says ‘freedom of information’ means choice of digital file format]
 +
* [http://blogs.perl.org/users/peter_martini/2014/08/the-chimera-quine-or-the-iso-pdf.html The Chimera Quine; or, the ISO PDF]
 +
* [http://openplanetsfoundation.org/blogs/2014-08-12-coming-preserving-pdf-identify-validate-repair-hamburg PDF info/links for attendees of conference on it]
 +
* [http://anjackson.github.io/keeping-codes/experiments/does-jhove-validate-pdfa-files Does JHOVE validate PDF/A files?]
 +
* [http://raywoodcockslatest.wordpress.com/2014/12/04/pdf-repair/ Methods of Repairing Corrupted or Damaged PDFs]
 +
* [http://stackoverflow.com/questions/17740175/how-do-i-dump-embedded-icc-profile-information-in-pdf-command-line-or-gui-tool/27464166#27464166 How do I dump embedded ICC profile information in PDF? (command line or GUI tools)]
 +
* [http://stackoverflow.com/questions/27938551/how-to-check-pdf-pages-for-resolution-dpi-of-embedded-images/27942530 How to check PDF pages for resolution (DPI) of embedded images?]
 +
* [http://chemxseer.ist.psu.edu/about/digital_library/das08-liu.pdf A Fast Preprocessing Method for Table Boundary Detection: Narrowing Down the Sparse Lines using Solely Coordinate Information]
 +
* [https://github.com/angea/PDF101/tree/master/handcoded/textextract Why text extracting doesn't work for all PDFs]
 +
* [http://stackoverflow.com/questions/29342542/how-can-i-extract-a-javascript-from-a-pdf-file-with-a-command-line-tool/29364036 How can I extract a JavaScript from a PDF file with a command line tool?]
 +
* [http://stackoverflow.com/questions/29331731/postscript-code-to-un-hide-hidden-text-in-pdf/29334742 How to un-hide hidden text in PDF]
 +
* [http://www.pdfa.org/2015/04/infographics-pdfua-and-wcag-2-0/ Infographics: PDF/UA and WCAG 2.0]
 +
* [http://www.prepressure.com/pdf/basics/history The history of PDF] according to prepressure.com, a site for "prepress & print devotees".
 +
* [https://isc.sans.edu/diary/Handling+Special+PDF+Compression+Methods/19597 Handling Special PDF Compression Methods]
 +
* [https://speakerdeck.com/ange/lets-write-a-pdf-file Let's write a PDF file]
 +
* [https://blog.didierstevens.com/2016/06/07/recovering-a-ransomed-pdf/ Recovering a ransomed PDF]
 +
* [https://github.com/digital-preservation/droid/issues/114 PDF version numbers based on deprecated mechanism]
 +
* [https://madfileformatscience.garymcgath.com/2016/09/26/pdf-version/ Figuring out the PDF version is harder than you think]
 +
* [https://www.pdfa.org/slides-and-video-recordings-of-the-pdf-days-europe-2017/ Slides and video recordings of the PDF Days Europe 2017]
 +
* [https://www.pcworld.com/article/2096946/5-cheaper-alternatives-to-acrobat-for-pdf-editing.html 5 cheaper alternatives to Acrobt for PDF editing]
 +
* [https://pdfraster.org/ PDF/raster site]
 +
* [https://www.pdfa.org/hunter-bidens-email-and-the-potential-for-deepfakes-with-pdf/ Hunter Biden’s “email” and the potential for deepfakes with PDF]
 +
* [https://www.bitsgalore.org/2021/09/06/pdf-processing-and-analysis-with-open-source-tools PDF processing and analysis with open-source tools]
 +
* [https://www.wowsignal.io/articles/pdf PDF cannot be tokenized]
 +
 +
[[Category:Page description languages]]
 +
[[Category:Adobe]]

Latest revision as of 14:09, 12 November 2024

File Format
Name PDF
Ontology
Extension(s) .pdf
MIME Type(s) application/pdf
LoCFDD fdd000030, others
PRONOM fmt/276, others
Wikidata ID Q42332

Portable Document Format (PDF) is a document file format originally from Adobe, based on PostScript. It has many subsets.

As well as the 'full function' ISO 32000-1:2008 (or PDF 1.7), there are also PDF/X, PDF/A, PDF/E, PDF/VT and PDF/UA, all of which are ISO specifications.

PDF profiles (formalized subsets) include the following:

  • PDF/A (optimized for preservation)
    • PDF/A-1 (ISO 19005-1:2005)
    • PDF/A-2 (ISO 19005-2:2011)
    • PDF/A-3 (ISO 19005-3:2012) (extends PDF/A-2 by allowing embedded files of any type)
    • PDF/A-4 (ISO 19005-4:2020)
  • PDF/E (ISO 24517-1:2008) (for engineering workflows)
  • PDF/UA (ISO 14289-1) (making documents accessible through assistive technologies)
  • PDF/VT (ISO 16612-2) (support for variable document printing)
  • PDF/X (support for prepress graphics exchange)
    • PDF/X-1 (ISO 15930-1:2001)
    • PDF/X-1a (ISO 15930-4:2003)
    • PDF/X-2 (ISO 15930-5:2003)
    • PDF/X-3 (ISO 15930-6:2003)
  • Tagged PDF

Some scanner documentation references an apparently fictitious "PDF/L" profile (see Gary McGath's "PDF/L?").

A PDF 2.0 spec (ISO 32000-2) was published in 2017-07, with some new features as well as clarification of conformance with existing features.

A PDF/raster draft spec was issued in 2017 as a subset of PDF files containing raster images of scanned documents.

Contents

[edit] Identifiers

Format PRONOM LoCFDD
PDF fdd000030
PDF 1.0 fmt/14 fdd000316
PDF 1.1 fmt/15
PDF 1.2 fmt/16
PDF 1.3 fmt/17
PDF 1.4 fmt/18 fdd000122
PDF 1.5 fmt/19 fdd000123
PDF 1.6 fmt/20 fdd000276
PDF 1.7 fmt/276 fdd000277
PDF 1.7, Ext. 3 fdd000313
PDF 2.0 fmt/1129
PDF/A fdd000318
PDF/A-1 fdd000125
PDF/A-1a fmt/95 fdd000251
PDF/A-1b fmt/354 fdd000252
PDF/A-2 fdd000319
PDF/A-2a fmt/476 fdd000320
PDF/A-2b fmt/477 fdd000322
PDF/A-2u fmt/478 fdd000321
PDF/A-3a fmt/479 fdd000360
PDF/A-3b fmt/480
PDF/A-3u fmt/481
PDF/A-4 fdd000532
PDF/X-1 fmt/144, fmt/145 fdd000124
PDF/X-1a fmt/157, fmt/146
PDF/X-2 fmt/147
PDF/X-3 fmt/158, fmt/148
PDF/X-4 fmt/488
PDF/X-4p fmt/489
PDF/X-5g fmt/490
PDF/X-5pg fmt/491
PDF/X-5n fmt/492
PDF/UA-1 fdd000350
PDF/E-1 fmt/493
PDF, Geospatial fdd000315
GeoPDF 2.2 fdd000312
PDF Portfolio fmt/1451

[edit] Identification

The majority of PDF files can be identified by a fixed header e.g. "%PDF-1.4", however, older documents have a number of variations.

[edit] Compression

Images in PDF documents may use the following compression schemes:

[edit] Digital Rights Management & Encryption

PDF has two types of 'encryption' - it uses an 'user' password to limit the ability to open the document, and a 'creator' password to limit other rights, like printing, copying, etc. The former case, where a password is required to open the file, is the main preservation concern, as our users will not be able to open a PDF encrypted in this way (unless the password can be cracked, which may be problematic both technically and legally). However, the latter case causes problems, because the PDF is encrypted here too, but with a special known user password of "" (an empty string, which is not the same as no password). So, the document is encrypted in both cases, and you can only tell which is which by attempting to decrypt the PDF using the special default password "". Some PDF analysis tools (notably JHOVE) do not implement the relevant decryption workflow, and so cannot distinguish between the two types of encryption.

An example of the decryption test workflow can be found here: https://gist.github.com/anjackson/5237071

Some of the most locked-up PDFs anywhere can be found at the ANSI IBR Standards Portal, which has made certain standards documents that are incorporated into legislation available for browsing, but only through a convoluted procedure involving downloading a special plug-in and filling out a registration form that must be re-filled-out in every browsing session.

A "Protected PDF" (PPDF) format is reportedly used by Microsoft's Azure Rights Management Service for sharing files securely within a workgroup.

[edit] Document redaction

Occasionally the attempts of technically-inept users to obscure content in PDF files get in the news. People have sometimes had the mistaken impression that if a section of text is overlayed with a solid-black shape, or set to white-on-white text, or some such thing, before the publicly distributed document is sent out, that would make the redacted sections unavailable; this is not true, as it is in fact easy to find text that has been obscured in such manners, often as simple as dragging a mouse over it to highlight it. This happened in a 2018 Florida case connected with the school shooting there, where some parts of the school district's report about the shooter were badly redacted and disclosed by a local newspaper, leading to a judge threatening punishment of the paper and prior restraint of future publications of theirs because of this "hacking", raising all sorts of legal and constitutional issues.

[edit] Web linking

When linked on the Web, specific pages of a PDF can be referenced by appending #page=N (where N is the desired page number) as a fragment identifier at the end of the URL. This is a little-known fact.

[edit] Specifications

[edit] Software

[edit] Online utilities

[edit] Sample files

[edit] See also

[edit] Links

[edit] Format info

[edit] Validation

[edit] Jailbreaking

[edit] Commentary

[edit] Miscellaneous

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