PDF/A, and which conformance level you actually need

PDF/A has three parts and several conformance levels, and the differences matter for whether a file will still open in twenty years. A plain guide.

21 September 2026 · Reference

PDF/A is a restricted profile of PDF, standardised as ISO 19005, designed so a document renders the same way in the future as it does today. It achieves that mostly by forbidding things.

What PDF/A forbids

• External dependencies — fonts must be embedded, colour must be defined against an embedded profile. Nothing the file needs may live outside it.
• Executable content — no JavaScript, no launch actions, no embedded executables.
• Encryption — an archived file must not need a password that will be lost.
• Non-deterministic rendering — no transparency in the strictest parts, no reliance on reader-specific behaviour.

The result is a file that carries everything required to render itself.

The parts and levels

Within A-1 through A-3 there are conformance levels:

Which PDF/A level should I use?

For most archiving, PDF/A-2b is the right default: it guarantees the appearance, and unlike A-1b it permits transparency, which nearly all modern design tools produce. Choose A-2u if the text must remain searchable, and A-2a only if you have an accessibility obligation — level A requires proper tagging, which is real work and cannot be added by a conversion tool.

Use A-1b only when a counterparty specifically demands it. Use A-3 when you genuinely need to carry a source file inside the PDF.

The PDF/A-3 attachment question

PDF/A-3's allowance for arbitrary attachments was controversial among archivists for an obvious reason: you can attach a file the standard cannot guarantee will be readable later, which undercuts the point. It exists largely because of electronic invoicing — the ZUGFeRD and Factur-X formats embed a machine-readable XML invoice inside a human-readable PDF, and that pairing needs A-3.

If you are not doing something of that shape, A-2 is the better choice.

Does PDF/A guarantee my document opens in twenty years?

It substantially improves the odds, and guarantees nothing. PDF/A removes the dependencies most likely to break — missing fonts, external colour profiles, scripts that assume a runtime — so the file is self-contained. What it cannot do is guarantee software will still exist to read it. That is why the format is paired with institutional practice: checksums, format migration and multiple copies. The standard solves the file; it does not solve the archive.

Validating, rather than trusting the export dialog

Exporting "as PDF/A" and being valid PDF/A are different claims. Producers get this wrong often enough that the archiving community maintains veraPDF, an open-source validator, as the reference implementation. If PDF/A compliance matters contractually, validate the output rather than trusting the checkbox.

What PDF/A costs you

• Files are larger, sometimes considerably, because everything is embedded
• No encryption, so confidentiality has to be handled by where you store it
• Level A demands tagging work that no automatic conversion does properly
• Transparency flattening in A-1 can visibly change a design

Which is a fair trade for a document meant to outlive the software that made it, and a poor one for a document somebody will read this week.