When you open a PDF the interpreter/reader 'just' computes the pages for you. As every byte counted then that language is Forth-like. So in a way it's similar to SVG, but internally based on PostScript a page description language from 40 years ago. PDF is actually meant to be a sealed container, providing impeccable typography (with embedded fonts even) and vector graphics, internal links and so on. It was awesome in its time and old habits die hard.
Why does the world use this insane file format?
