Concept Definition
What is PDF/A-3?
PDF/A-3 is an ISO 19005-3 standardized subset of PDF optimized for long-term archiving. Unlike PDF/A-1 and PDF/A-2, PDF/A-3 permits embedding arbitrary file attachments including XML files. This capability is exploited by Factur-X and ZUGFeRD to embed CII XML inside a visually compliant PDF document.
How do PDF/A versions differ?
PDF/A has three versions, each with increasing capabilities:
- PDF/A-1: No embedded files. Most restrictive. Based on PDF 1.4.
- PDF/A-2: No embedded files. Adds JPEG2000, transparency, layers. Based on PDF 1.7.
- PDF/A-3: Allows embedded file attachments of any type. Basis for Factur-X and ZUGFeRD.
Frequently Asked Questions
- Why does Factur-X use PDF/A-3?
- Factur-X requires a PDF container that supports embedded file attachments (for the CII XML) and meets long-term archiving requirements. PDF/A-3 is the only PDF/A version that allows arbitrary embedded attachments while maintaining archival integrity.
- Is a PDF/A-3 file the same as a regular PDF?
- PDF/A-3 files can be opened in any standard PDF reader. However, they must conform to specific restrictions (no encryption, embedded fonts, color profiles) that ensure they remain readable over time. Not all PDFs created by standard tools are PDF/A-3 compliant.