You scan a lease agreement, a notarial deed, or payslips to keep them. A few years later, you open the file — and find fonts that no longer display correctly, missing images, a broken interactive layer.
That's exactly the problem PDF/A solves since 2005. Here's what to know before archiving important documents.
PDF/A in one sentence
PDF/A (ISO 19005) is a PDF variant designed to guarantee perfect readability of a document over the very long term, regardless of the software or system that opens it 30 years from now.
Concretely, a PDF/A is a PDF with additional constraints:
- All fonts must be embedded (no reference to a system font)
- No external content (no URL-linked images, no JavaScript, no active forms)
- No encryption (the file must be openable by any reader)
- Standardized metadata (XMP, RDF) for archive classification
- Closed color spaces (no proprietary ICC profile)
In short: a PDF/A is self-contained. Everything it needs to display correctly is in the file.
Why a "regular" PDF isn't enough
A regular PDF can reference:
- A system-installed font — which may not exist in 20 years
- An external link to a third-party PDF — whose URL will have changed
- An embedded Flash plugin — whose format died in 2020
- A specific color profile from a 2003 printer
When you open it in 2050, the application will display "default font" instead of the original, the image will be missing, the form will no longer work.
For a temporary marketing document, no problem. For a decade-retention contract, notarial deed, or accounting archive, that's unacceptable.
PDF/A levels: 1, 2, 3
Three main families, each with two conformities (a and b).
PDF/A-1 (2005)
The original standard. Doesn't support transparency, layers, or modern OpenType fonts.
- PDF/A-1a: strict, accessible (Tagged PDF — useful for screen readers)
- PDF/A-1b: visual conformity only (rendering will be identical, but not necessarily accessible)
PDF/A-2 (2011)
Supports JPEG2000, transparency, layers, and embedding PDF/A inside PDF/A.
- PDF/A-2a: strict + accessible
- PDF/A-2b: visual only
- PDF/A-2u: visual + guaranteed-searchable text (Unicode)
PDF/A-3 (2012)
Like PDF/A-2 but allows embedding arbitrary files (CSV, XML, original Word). Heavily used for electronic invoices: visual PDF + structured XML in a single file.
- PDF/A-3a / 3b / 3u (same nuances as PDF/A-2)
Which to choose?
| Use case | Recommended level |
|---|---|
| Simple archive (contract, quote) | PDF/A-1b |
| Archive with accessibility (public admin) | PDF/A-1a or PDF/A-2a |
| Modern PDF with transparency/layers | PDF/A-2b |
| Electronic invoice (Factur-X, ZUGFeRD) | PDF/A-3 |
| Academic publication | PDF/A-2u or PDF/A-3u |
For 95% of cases, PDF/A-2b is the ideal compromise: modern, broad compatibility, reasonable size.
When PDF/A is legally mandatory
A few European contexts where PDF/A is required:
- French public archives: required by SIAF (Interministerial Service of French Archives)
- Dematerialized public tenders: most platforms accept only PDF/A
- Factur-X / ZUGFeRD (FR + DE electronic invoice standard): mandatorily PDF/A-3 based
- Commercial court registries: annual accounts deposits in PDF/A
- Probative archiving (eIDAS, AFNOR NF Z42-013 certification): PDF/A-1 or PDF/A-2 mandatory for legal value
How to verify a PDF is really PDF/A
Three methods:
1. XMP metadata
Open the PDF with a metadata-capable editor (Adobe Acrobat, or Sumatra). PDF/A files declare in their metadata:
pdfaid:part = "2"
pdfaid:conformance = "B"
2. veraPDF (free open-source validation)
veraPDF is the reference tool to validate PDF/A conformity. Open-source, multiplatform, required by professional archivists.
3. PDFly (simple verification)
When converting to PDF/A on PDFly, the generated file is validated by the engine — you have the guarantee that the output is conformant.
How to convert a regular PDF to PDF/A
Several options depending on context:
Online — PDFly Premium
- Go to pdfly.eu/en/tools/pdf-to-pdfa
- Drop your PDF
- Choose the level (PDF/A-1b, 2b, 2u recommended)
- Download the result
This is a Premium feature (€4.99/month) because conversion requires server processing (embedding missing fonts, ISO verification). The file is deleted immediately after download.
Local software — Adobe Acrobat
File → Save As → choose "PDF/A" in dropdown. Included in Adobe Acrobat Pro (≈ €19/month).
Command line — Ghostscript
Free and powerful for advanced uses.
gs -dPDFA=2 -dBATCH -dNOPAUSE -sDEVICE=pdfwrite \
-sOutputFile=archive.pdf source.pdf
Advantage: scriptable, ideal to convert 1,000 files in batch.
Common pitfalls to avoid
- Converting an already-signed PDF to PDF/A — the digital signature can be invalidated. Convert first, sign after.
- PDF/A with interactive content — JavaScript forms break on conversion. Save the active form separately.
- PDF/A without validation — always validate with veraPDF before legal archiving.
- PDF/A-3 for simple archive — overkill, choosing A-1b or A-2b is enough in 95% of cases.
In summary
PDF/A isn't an administrative gadget: it's a technical guarantee of readability over 30 or 50 years, legally required in several European contexts.
For most professional archives: PDF/A-2b is the ideal modern standard. Conversion takes less than a minute, but the benefit runs for decades.
Convert your PDFs to PDF/A now with PDFly Premium — no commitment, EU-hosted.