PageMagic is a mid-1990s desktop publishing program for Windows published by NEBS. It used the extension .dtp, but its files were not compatible with Timeworks Publisher (also known as Publish It!), even though that program used the same extension.
The format appears to be a variety of the OLE2 Microsoft Compound File. This provides a manner of distinguishing these files from the similarly-named Timeworks/Publish It! files; detection software such as DROID may detect PageMagic files as OLE2 while the other program's files do not detect this way.