[Someone]

The standards related to PDF are open. https://en.wikipedia.org/wiki/PDF:

”PDF was standardized as an open format, ISO 32000, in 2008, and no longer requires any royalties for its implementation”

Also, https://en.wikipedia.org/wiki/PDF#Intellectual_property:

”Anyone may create applications that can read and write PDF files without having to pay royalties to Adobe Systems; Adobe holds patents to PDF, but licenses them for royalty-free use in developing software complying with its PDF specification.”

It’s a huge spec, though. For example, fully supporting PDF requires a JavaScript engine.

[tonyedgecombe]

and half a dozen image formats, font formats, bits of PostScript, I think there is even some XML lurking in there.