XML embedded in a PDF/A-3

PDF/A-3 is the archival standard that allows a structured XML inside the PDF, the foundation of the hybrid invoice.

Definition

PDF/A-3 is a version of the PDF/A archival standard (ISO 19005) that, unlike earlier versions, allows arbitrary files to be embedded as attachments, including a structured XML file. The document remains a readable, durably archivable PDF while carrying machine-processable data.

How it works

• The PDF displays the human-readable invoice.
• An XML file (for example a Factur-X or ZUGFeRD file) is attached inside the same file.
• The PDF metadata declares the presence and role of the attached file, letting software locate it automatically.

Good to know

This embedding mechanism is precisely what distinguishes a hybrid invoice from a plain PDF: the internal XML carries the structured data while PDF/A-3 guarantees readability and long-term archiving.