PDF/A

PDF/A is a version of PDF built for long-term archiving, defined by the ISO 19005 standard. The idea is simple: a document you save today should open and look identical decades from now, even when the original software is long gone. Archives, courts, and government bodies often require it for exactly that reason.

What makes a file PDF/A is mostly about being self-contained. Every font must be embedded, color has to be unambiguous, and anything that depends on external resources or could change over time, like JavaScript, audio, or links to outside files, is banned. The document carries everything it needs to render itself.

There are several conformance levels (PDF/A-1, -2, -3, and sub-levels a/b/u) that trade strictness for features. If you are saving records you have to keep for years, converting to PDF/A is what protects them from becoming unreadable later.