Embedded fonts

Embedded fonts are typefaces packaged inside the PDF itself rather than borrowed from the computer that opens it. This is the feature that makes PDF genuinely portable: if the font travels with the document, the text renders identically everywhere, even on a machine that has never had that typeface installed.

When a font is not embedded, the reader has to substitute a similar one, and the result drifts, line breaks move, spacing changes, and a carefully laid-out page can reflow into something the author never approved. To avoid bloat, PDFs usually embed a subset: only the specific glyphs the document actually uses are stored, so a file that uses a handful of characters from a large family stays small. Fonts can be embedded as TrueType, Type1 or CFF/OpenType programs.

Embedding is mandatory for archival profiles like PDF/A and print profiles like PDF/X, precisely because a self-contained file must not depend on what happens to be installed elsewhere. When you rebuild or optimise a PDF, handling fonts correctly is what keeps the page looking the way it was designed, on any device and offline.