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PDF/A-3

ISO-standardised archival PDF format that allows embedding arbitrary file attachments — the container used by ZUGFeRD and Factur-X.

PDF/A-3 is a subset of PDF defined by ISO 19005-3 for long-term archiving. Unlike earlier PDF/A variants, PDF/A-3 permits embedding arbitrary file attachments within the PDF container — a capability exploited by ZUGFeRD and Factur-X to attach a structured XML invoice alongside the human-readable document.

The result is a single hybrid file: open it in any PDF viewer to see the formatted invoice; feed it to an ERP to extract and process the XML attachment automatically.

Key facts

  • Standard: ISO 19005-3
  • Key difference from PDF/A-1/2: allows arbitrary embedded file attachments
  • Used by: ZUGFeRD, Factur-X
  • XML attachment name in ZUGFeRD: factur-x.xml (v2.x) or ZUGFeRD-invoice.xml (v1.x)
  • Relationship type must be set to Alternative, Source, or Data in the PDF file spec