The problem PDF/A solves
A normal PDF can depend on things outside the file: fonts installed on your computer, colours that depend on your screen, links to websites, video players and scripts. Today, that's fine. In 30 years, the font might not exist and the link might be dead.
PDF/A (the A stands for archive) is a restricted version of PDF, defined in the international standard ISO 19005. It requires everything needed to display the document to be inside the file, and bans features that could stop it opening in future.
What PDF/A requires and forbids
| Requirement | Why |
|---|---|
| All fonts embedded | Text looks the same on any device, forever |
| Colour defined with an embedded profile | Colours stay accurate |
| Standard XMP metadata | Archives can catalogue the file |
| No encryption or passwords | Future archivists must be able to open it |
| No JavaScript, audio or video | These may not be supported in future |
| No links to external content | External sources disappear |
The versions
| Version | Year | Based on | Key points |
|---|---|---|---|
| PDF/A-1 | 2005 | PDF 1.4 | The original; no transparency or layers |
| PDF/A-2 | 2011 | PDF 1.7 | Allows transparency, layers, JPEG 2000 and embedded PDF/A files |
| PDF/A-3 | 2012 | PDF 1.7 | Like A-2, but can embed any file type, e.g. the original spreadsheet or XML invoice data |
| PDF/A-4 | 2020 | PDF 2.0 | Simplified levels; built on the latest PDF standard |
Conformance levels
Each version comes in levels, shown by the letter after the number:
- b (basic): the document will look the same in future. The minimum level.
- u (Unicode): like b, plus all text is mapped to Unicode, so it can be reliably searched and copied.
- a (accessible): like u, plus the document is tagged with structure and reading order for assistive technology.
PDF/A-4 replaces these with a base level plus PDF/A-4e (for engineering documents with 3D content) and PDF/A-4f (allowing embedded files).
So "PDF/A-2b" means: version 2, basic level.
Who needs PDF/A?
- Courts and legal filings: many court e-filing systems require or recommend PDF/A.
- Government records and public archives: national archives often specify it for long-term preservation.
- Universities: many require theses and dissertations in PDF/A.
- Regulated industries: finance, healthcare and engineering records with long retention periods.
- E-invoicing: standards such as ZUGFeRD and Factur-X use PDF/A-3 to embed machine-readable invoice data.
If nobody has asked for PDF/A, a normal PDF is fine for everyday use.
How to create a PDF/A file
The most reliable route is to export from the original document:
- Microsoft Word: File → Save As → PDF → Options → tick "PDF/A compliant".
- LibreOffice: File → Export as PDF → tick "Archive (PDF/A, ISO 19005)" and choose the version.
- Adobe Acrobat Pro: Save As Other → Archivable PDF (PDF/A), or use the Preflight tool to check and fix.
Converting an existing PDF afterwards is harder, because missing fonts may not be available. After creating a PDF/A file, check it with a validator such as the free, open-source veraPDF, which is endorsed by the PDF Association.
Before you convert
- Keep your original. Some features, such as forms with scripts or embedded media, will be removed.
- Remove passwords first with Unlock PDF, because PDF/A can't be encrypted.
- Scanned documents should go through OCR first, if you want them to be searchable at level u or a.
Frequently asked questions
Can I password-protect a PDF/A file?
No. Encryption is forbidden in PDF/A, because a future archivist might not have the password. Store PDF/A files in a secure system instead.
Is PDF/A bigger than a normal PDF?
Often slightly, because all fonts must be embedded. The difference is usually small.
Which PDF/A version should I use?
Use whatever your court, university or records office asks for. If there's no requirement, PDF/A-2b is a widely accepted choice; PDF/A-2u or A-3u if you want text to be reliably searchable.
Does saving as PDF/A make a file accessible?
Not by itself. Only level a (accessible) requires tags and reading order. Accessibility is covered by PDF/UA.