@Pi_rat The base format is a free format, with documentation and there are several fully free pdf implementations, so pdf is a fine format.

adobe of course has added a bunch of proprietary extensions, some of which has been reverse engineered.


A potential issue is that adobe has patents restricting the format, although they do grant them to anyone who has a fully "standards compliant" implementation.

Such issue appears to only really apply to proprietary viewers and producers, as mupdf, ghostcript and poppler appear to meet the base standard and also implement some extensions.

"adobe reader" is know for sometimes producing pdfs that are sabotaged on any other viewer, although GNU ghostcript can repair such pdfs.


pdf is a good format for viewing-only purposes, as you can be confident that it will display the same anywhere (although some proprietary viewers have issues like not implementing pdf links), but good luck editing it (this sometimes isn't a problem - very limited edits in some documents are possible via a text editor and libreoffice can embed .odt files into pdfs and you can embed the .tex file(s) into the pdf with pdflatex).