What is PDF/A?
A PDF that will open the same way in thirty years: no fonts borrowed from your computer, no external content, no passwords.
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What PDF/A means
PDF/A is an ISO standard (ISO 19005) for the long-term preservation of electronic documents. A PDF/A is a regular PDF with extra rules: everything needed to render it must be inside the file, and anything that could change its appearance over time is forbidden. The «A» stands for archive.
The first version was published in 2005; three more followed. They are compared in the guide to PDF/A versions.
How PDF/A differs from a normal PDF
| Regular PDF | PDF/A | |
|---|---|---|
| Fonts | May rely on fonts installed on the computer | All embedded in the file |
| Colours | May depend on the device | Defined by an embedded colour profile |
| Passwords and encryption | Allowed | Forbidden |
| JavaScript, audio, video | Allowed | Forbidden |
| External content | Can be referenced | Forbidden |
| Metadata | Optional | Required, in XMP |
On screen a good PDF/A usually looks identical to the original. What changes is what is inside the file.
What “PDF/A compliant” means
A file is PDF/A compliant when it follows every rule of the version it declares. The declaration itself is just a line in the metadata, so it proves nothing on its own: plenty of files say «PDF/A-1b» and are not. Only a validator, which checks the file rule by rule, can tell. You can run one on any file with our PDF/A validator.
The versions in short
- PDF/A-1 (2005) — based on PDF 1.4; no transparency or layers.
- PDF/A-2 (2011) — based on PDF 1.7; allows transparency, layers and JPEG 2000.
- PDF/A-3 (2012) — like PDF/A-2, plus attachments of any format.
- PDF/A-4 (2020) — based on PDF 2.0.
The letter after the number is the conformance level: b preserves the appearance, a also requires a tagged, accessible structure, u requires all text to be extractable as Unicode.
Frequently asked questions
What is a PDF/A file?
A PDF that conforms to ISO 19005, the standard for long-term preservation: it embeds every font and colour profile it needs and contains no passwords, JavaScript or external content.
What does PDF/A compliant mean?
That the file follows every rule of the PDF/A version it declares. The declaration alone proves nothing: a validator has to check the file rule by rule.
Is PDF/A editable?
Technically yes, but any edit can break compliance, so readers such as Acrobat open PDF/A files read-only. If you need to edit one, remove the PDF/A declaration first with PDF/A to PDF.
What is PDF/A mode in Acrobat?
A read-only view Acrobat uses when a file declares PDF/A, to stop accidental changes. It can be switched off; see PDF/A mode in Acrobat.