Courts, government portals, universities and e-invoicing systems increasingly ask for PDF/A, the archival version of PDF. If a portal rejects your upload with "file must be PDF/A", here is how to convert it and check the result.
Which PDF/A version do you need?
PDF/A comes in parts and conformance levels:
- PDF/A-1b: the oldest and strictest; no transparency, no embedded files. Some legacy systems still require it.
- PDF/A-2b: allows transparency, layers and JPEG 2000 compression. The best general-purpose choice.
- PDF/A-3b: like 2b, but allows embedded files of any type. Used by hybrid e-invoices such as Factur-X.
- "a" levels (such as PDF/A-2a) additionally require tagging for accessibility.
- "u" levels require text to be mapped to Unicode, which helps search.
If the requirement just says "PDF/A", PDF/A-2b is usually accepted. If it names a version, use exactly that one. See PDF/A archival format explained.
Method 1: export from Word or LibreOffice
The cleanest PDF/A comes from the source document.
- Word (Windows): File → Save As → PDF → Options → tick PDF/A compliant.
- LibreOffice: File → Export as PDF → General tab → tick Archive (PDF/A, ISO 19005) and choose the version.
Method 2: Adobe Acrobat Pro
Open the PDF, go to the PDF Standards tool (or Save as Other → Archivable PDF (PDF/A)), pick the version and save. Acrobat fixes many issues automatically, such as embedding fonts.
Method 3: Ghostscript (free, command line)
gs -dPDFA=2 -dBATCH -dNOPAUSE -dPDFACompatibilityPolicy=1 \
-sColorConversionStrategy=RGB -sDEVICE=pdfwrite \
-o output-pdfa.pdf input.pdf
For full conformance Ghostscript also needs a PDFA definition file with an output intent (ICC colour profile). Treat the output as a candidate and validate it. See Ghostscript introduction.
Always validate
A file that claims PDF/A is not necessarily compliant. Run it through a validator:
- veraPDF: free, open source, and the reference validator endorsed by the PDF Association.
- Acrobat Preflight: built into Acrobat Pro.
Fix any reported errors and validate again before submitting.
What commonly blocks conversion
- Fonts that cannot be embedded due to licensing. Substitute a different font in the source.
- Encryption or passwords. PDF/A forbids encryption. Remove protection first. See how to remove a password from a PDF.
- JavaScript, audio, video or external links to content. These are not allowed and will be removed or block conversion.
- Transparency in PDF/A-1. Use PDF/A-2 if you can, or flatten transparency. See PDF transparency flattening explained.
- Digital signatures. Converting a signed PDF breaks the signature. Convert first, then sign.
Order of operations
- Finish editing (merge, reorder, add page numbers).
- Convert to PDF/A.
- Validate.
- Sign, if required, with a PDF/A-aware signing tool.
- Do not edit again.
Editing steps before conversion can be done in a browser tool such as Docento.app without uploading your files.
Takeaway
Use PDF/A-2b unless told otherwise, export from the source document when possible, and always validate with veraPDF before submitting. Convert before signing, never after.
