Why regulators ask for PDF/A, what conformance levels mean, and what gets stripped when you convert.
PDF/A exists to answer one question: will this file still render identically in forty years, on software that does not exist yet? Ordinary PDF cannot promise that, because it can reference resources it does not contain.
The core rule: self-containment
A PDF/A file must carry everything it needs inside itself. Every font fully embedded. Every colour space explicitly defined rather than device-dependent. No external references, no JavaScript, no audio or video, no encryption, no transparency in the older levels. If the file needs something from outside itself to render, it is not PDF/A.
Conformance levels, briefly
- Level B (basic): guarantees the visual appearance is reproducible. This is the common requirement and the easy one to meet.
- Level A (accessible): adds structural tagging, logical reading order and Unicode mapping — so the document is machine-readable and accessible to screen readers, not just visually faithful.
- Level U: level B plus Unicode text mapping, without full structural tagging. A useful middle ground when text extraction matters but full tagging is impractical.
Versions PDF/A-1 through PDF/A-4 differ mainly in what they permit: A-1 is the strictest and forbids transparency and layers; A-2 and A-3 relax that and allow embedded attachments; A-3 notably allows arbitrary embedded files, which is how e-invoicing standards ship XML inside a human-readable PDF.
What conversion strips
- Encryption and permissions — archival formats must be openable without a key.
- Embedded multimedia and JavaScript.
- Non-embedded fonts, which get substituted or embedded from a system equivalent. Watch for reflowed line breaks here.
- External hyperlinks may survive as text but stop being guaranteed to resolve.
- Transparency effects, in PDF/A-1, which get flattened into composited images.
When you genuinely need it
Court filings, regulatory submissions, tax records, institutional repositories, and any document with a legally mandated retention period. If nobody has asked for PDF/A, you probably do not need it — the constraints cost you features for a benefit measured in decades.
Validate, do not assume
A file being produced by a PDF/A converter is not proof it conforms. Run it through a validator and check for the conformance claim in the XMP metadata. Submissions get rejected on this constantly, usually for one non-embedded font in a footer nobody looked at.
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