From Just Solve the File Format Problem
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File Format
Name PDF
Extension(s) .pdf

PDF, portable document format, based on PostScript and originally from Adobe, 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/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

Also see: extension PDF


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 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:

Sample files


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