Early PDF was quite sane. It was the Postscript imaging model turned into a binary bytecode format with almost all the programmability features removed.
Later on it got wonky (though never even close to the extent to which Flash did!) with all the hypertextification features. But basic PDF is actually one of the Great File Formats in computer history.
I didn't realize that this standard existed. Thanks for the link, that's very helpful to know. I've always viewed "modern PDF" as an ad hoc thing defined by the intersection of whatever was supported by the popular free renderers.
Later on it got wonky (though never even close to the extent to which Flash did!) with all the hypertextification features. But basic PDF is actually one of the Great File Formats in computer history.