[mannyv]

The original goal of PDF was to have a portable print fidelity copy; WYSIWYG for real. You could take a PDF file and print it on a laser printer, a linotype, or a screen and it would look the same.

If you printed it on a postscript printer it would look exactly the same (or better, if you used type 1 fonts).

[mannyv]

PDF is pretty much a symbolic representation of what needs to be printed out. It's symbolic so it can get rasterized onto whatever device in question, in a way that should be as accurate as possible to a print version.

That's the primary requirement of PDF, and has been since the beginning.

They added a bunch of interactive stuff to it, which are used occasionally (forms). But to understand PDF you need to understand the above first.