So USB 1.0, 1.1 and 2.0 were just imagined then?
What about Bluetooth 1.0, 1.0A, 1.0B, 1.1, 1.2, 2.0 and 2.1?
No such thing as "different versions"? Sorry, but you're very wrong.
There have been nine versions of the PDF file format, with corresponding Acrobat releases for each. Version 1.4 is the basis for the ISO standards for PDF/X and PDF/A and PDF documents conforming to ISO 32000 carry the PDF version number 1.7. See
http://en.wikipedia.org/wiki/Portable_Document_Format for further enlightenment and edification.
So, again, I will ask: which PDF file format version do these files claim to be?