PDF Reference Manual (Version 1.0)

TL;DR — The original 1993-era PDF reference in its Addison-Wesley printing — the format before it was a standard.

Adobe Systems / Addison-Wesley.

The first PDF reference, against PDF 32000-1:2008 — The PDF Specification’s 756 pages fifteen years later. The pairing is the point: you can read the format’s whole expansion by putting the two side by side — what PDF was when it was a page-description container, and what it became once forms, encryption, tagging and JavaScript were bolted on.

A good short study in how a format accretes.

Where this came from

• Will Manidis’s “most underrated PDF” thread

230 pages. A copy is archived locally against link rot; the header links the original source.