What Is PDF/A-3?
PDF/A-3 is an ISO standard (ISO 19005-3:2012) that defines a variant of the PDF format specifically designed for long-term digital preservation and archiving. It belongs to the PDF/A family of standards, which impose strict requirements on PDF files to ensure they remain readable and visually consistent over decades, independent of the software or hardware used to create them.
What makes PDF/A-3 unique within the PDF/A family is its ability to embed arbitrary file attachments. While earlier versions (PDF/A-1 and PDF/A-2) were focused purely on the visual document, PDF/A-3 allows additional files of any format to be attached inside the PDF container. This capability is precisely what makes Factur-X possible.
PDF/A-3 and Factur-X
The Factur-X e-invoicing standard relies entirely on PDF/A-3 as its container format. A Factur-X invoice is, technically, a PDF/A-3 document with a CII XML file embedded as an attachment. This creates the hybrid nature that makes Factur-X so practical:
- The PDF layer: A human-readable, visually formatted invoice that can be opened with any PDF viewer. It contains the familiar layout of an invoice with company logos, addresses, line items, and totals.
- The XML attachment: A machine-readable CII XML file that contains all the structured invoice data. This is what accounting software and certified platforms (PDPs) extract for automated processing.
The PDF/A-3 specification ensures that both layers coexist within a single file, eliminating the need to manage separate PDF and XML files.
Key Characteristics of PDF/A-3
Long-Term Preservation
PDF/A-3 files are self-contained. All resources needed to render the document, including fonts, color profiles, and images, are embedded within the file. This means the document will look identical whether opened today or in 50 years, on any compliant reader.
Font Embedding
All fonts used in the document must be embedded. This prevents display issues that occur when a system does not have the required font installed, a common problem with regular PDFs.
No External Dependencies
PDF/A-3 files cannot reference external content (URLs, linked images, embedded scripts, or multimedia). This restriction ensures that the document is fully self-contained and not dependent on external resources that might become unavailable.
Metadata
PDF/A-3 requires XMP (Extensible Metadata Platform) metadata, providing standardized document properties such as author, creation date, and description. For Factur-X documents, this metadata also includes the Factur-X profile level and conformance information.
File Attachments
The defining feature of PDF/A-3: it allows files of any format to be attached. In the Factur-X context, the attachment is always a CII XML file (named factur-x.xml), but the standard does not restrict the type or number of attachments.
PDF/A-3 vs. Other PDF/A Versions
| Version | ISO Standard | Year | Attachments | Use Case |
|---|---|---|---|---|
| PDF/A-1 | ISO 19005-1 | 2005 | None | Basic archival |
| PDF/A-2 | ISO 19005-2 | 2011 | PDF/A files only | Enhanced archival |
| PDF/A-3 | ISO 19005-3 | 2012 | Any file type | Hybrid documents (Factur-X) |
Only PDF/A-3 supports embedding non-PDF attachments, which is why it was chosen for Factur-X.
Why PDF/A-3 Matters for French E-Invoicing
Legal Archival Requirements
French law requires businesses to retain invoices for at least 10 years. PDF/A-3 was designed for exactly this purpose: guaranteeing long-term readability without dependence on specific software versions.
Compliance Validation
When the PPF or a PDP receives a Factur-X invoice, it validates not only the CII XML content but also the PDF/A-3 conformance. A document that fails PDF/A-3 validation (for example, because fonts are not embedded or external references are present) may be rejected.
Backward Compatibility
Because the outer layer is a standard PDF, recipients who have not yet adopted automated processing can still open, print, and read the invoice. This makes PDF/A-3 an ideal bridge format during the transition period of the 2026 reform.
Practical Implications
For businesses using billing platforms like Stripe, generating proper PDF/A-3 documents requires specialized tooling. Standard PDF generators often produce regular PDFs that do not meet PDF/A-3 requirements (missing embedded fonts, external references, non-compliant metadata). A dedicated Factur-X generation service handles these technical requirements, ensuring that the output PDF meets ISO 19005-3 specifications and that the embedded CII XML is correctly attached and referenced in the document metadata.