The Tip of the Night for September 25, 2015, discussed the new standard filing format, PDF/A which allows for legal filings to digitally archived. If you’ve used Adobe Acrobat to save documents as PDF/A files you may have noticed that there are several different PDF/A types to choose from.
In Acrobat, if you go to File . . . Save as Other . . . Archivable PDF (PDF/A),
. . . .you will see that you have an option of eight different PDF/A options.
What is the difference between these?
PDF/A-1a bars the inclusion of audio or video files, and also prohibits the use of Java script or executable files. Encryption can also not be used, and fonts have to be embedded. PDF/A-1b differs from PDF/A-a in that it does not require that the 'logical structure' of a document be represented. So this Level B conformance can add in structural or source material not present in the source material.
PDF/A-2 files can include transparent layers, allow for JPEG 2000 compression, and have additional provisions for digital signatures. Crucially this standard also permits other PDF/A-2 files to be embedded in parent PDF/A-2 files. PDF/A-2a requires the logical structure be maintained, whereas PDF/A-2b does not. PDF/A-2u has to be exclusively in Unicode text, but does not need to have the logical structure of the source document.
PDF/A-3 allows the embedding of other files such as Word and Excel files in the archived PDF. In turn, PDF/A-3a retains the logical structure of the source; PDF/A-3b does not; and PDF/A-3u must use Unicode text.