Tables to look things up in: every operator, filter, color space, blend mode, font type, annotation, action and structure type, with the version that added it and where the specification defines it.
Each table marks what was added after PDF 1.0 with the version that added it, and links to where PDF 1.4 (Adobe PDF Reference, 3rd ed.) and PDF 1.7 (ISO 32000-1) define it. To learn how the pieces fit together first, start with Learning.
Graphics
OperatorsAll 73 content-stream operators with their operands, grouped as the specification groups them, and where each may appear.Color spacesThe eleven color space families, their components and initial colors, and how each is written in a file.Blend modesThe sixteen standard blend modes, separable and non-separable, with the formula for each.
Text
Font typesEvery font dictionary subtype, the font programs that can be embedded for each, and the encodings simple fonts use.Standard 14 fontsThe fonts a PDF can use without embedding them, their built-in encodings, and why to embed them anyway.
Files
Interactive
Annotation typesEvery annotation subtype, whether it is a markup annotation, and the version that added it.Action typesEvery action type, what it does, and the triggers that can run one.