PDF/A explained: when you need it and what it changes
PDF/A in plain language: what PDF/A-1, -2 and -3 and the "a"/"b" levels mean, who requires it, and how to check that a file really conforms.
By Fileixa editorial team, Creates Online LLC · Published · 6 min read
The problem PDF/A solves
A normal PDF can depend on things outside the file: fonts installed on the computer, colour settings of a device, links to external content, even scripts. Open it in 20 years on different software and it may not look the same, or open at all. PDF/A (ISO 19005) is a stricter version of PDF designed so a document can be reproduced exactly, indefinitely.
What a PDF/A file must contain
In practice this means:
- Every font used is embedded in the file.
- Colours are defined in a device-independent way, with an embedded colour profile (output intent).
- No encryption or passwords, and no JavaScript, audio or video.
- Standard XMP metadata describing the document and the PDF/A level it claims.
The versions and levels
PDF/A-1 (2005) is the oldest and strictest. PDF/A-2 (2011) is based on a newer PDF version and allows JPEG 2000 compression, transparency and layers; it is the most widely requested today. PDF/A-3 additionally allows any file to be embedded, which e-invoicing standards use to attach XML data.
The letter after the number is the conformance level. "b" (basic) guarantees the visual appearance will be preserved. "a" (accessible) also requires a tagged structure for screen readers and text extraction. "u" (Unicode) requires that all text maps to Unicode.
Who asks for it
Court e-filing systems, national archives, public-sector records departments, some universities for theses and many companies for contracts and invoices they must retain for years. Always check which version and level they require; PDF/A-2b is the most common.
Conversion is not the same as validation
Converting a PDF to PDF/A embeds the fonts, converts colours and writes the required metadata, and the result will usually be accepted. But only a validator can prove conformance. If a strict archive rejects a file, run it through a validator such as the free, open-source veraPDF, which lists exactly which rule failed.