PDF/A Format with Embedded XML for Peppol: Requirements and How to Fix

You attached a PDF to your Peppol invoice and got an error: "invoices must be in PDF/A format with embedded XML." This means your PDF does not comply with the PDF/A archival standard that Peppol requires for document attachments. Here is what PDF/A is, why Peppol requires it, and how to fix the error.

What is PDF/A?

PDF/A (ISO 19005) is a specialized version of PDF designed for long-term digital preservation. Unlike regular PDFs, PDF/A files are completely self-contained. All fonts are embedded. JavaScript is prohibited. External references are not allowed. Color profiles are mandatory. This ensures the document will render identically on any system, now and decades from now.

PDF/A versions explained

There are three main versions of PDF/A. The version you need depends on what you are doing:

Hybrid invoices: Factur-X and ZUGFeRD

A hybrid invoice combines both worlds: a human-readable PDF and a machine-readable XML in a single file. The PDF/A-3 format makes this possible by allowing the XML to be embedded as an attachment inside the PDF.

Two standards use this approach:

• Factur-X (France/Germany joint standard): Embeds a CII (Cross Industry Invoice) XML file named factur-x.xml inside a PDF/A-3 document.
• ZUGFeRD 2.x (Germany): Technically identical to Factur-X. The XML file is named factur-x.xml (since ZUGFeRD 2.0 aligned with Factur-X).

These hybrid formats are gaining traction in Europe because they bridge the gap between human and machine processing. The recipient can view the PDF like a traditional invoice, while automated systems extract the XML data. Read our ZUGFeRD format guide for more details on profiles and implementation.

When does Peppol require PDF/A?

Peppol BIS Billing 3.0 allows you to attach additional documents to an invoice using the AdditionalDocumentReference element. When you embed a PDF representation of the invoice, many access points require PDF/A format. This is especially true for:

• Invoice visual representations attached to UBL invoices
• Supporting documents (contracts, delivery notes) attached as PDFs
• Hybrid invoice workflows where Factur-X/ZUGFeRD documents are converted to Peppol UBL

How to attach a PDF/A to a Peppol invoice

In UBL, you attach the PDF/A using the AdditionalDocumentReference element with the document embedded as base64:

<cac:AdditionalDocumentReference>
  <cbc:ID>Invoice-PDF</cbc:ID>
  <cbc:DocumentDescription>
    Invoice visual representation
  </cbc:DocumentDescription>
  <cac:Attachment>
    <cbc:EmbeddedDocumentBinaryObject
      mimeCode="application/pdf"
      filename="invoice-2026-001.pdf">
      <!-- Base64-encoded PDF/A content -->
      JVBERi0xLjQKJeLjz9MKMSAwIG9iago...
    </cbc:EmbeddedDocumentBinaryObject>
  </cac:Attachment>
</cac:AdditionalDocumentReference>

How to convert PDF to PDF/A

If your system generates regular PDFs, you need to convert them to PDF/A before attaching to a Peppol invoice. Here are the most common approaches:

gs -dPDFA=3 -dBATCH -dNOPAUSE -dNOOUTERSAVE \
   -sColorConversionStrategy=UseDeviceIndependentColor \
   -sDEVICE=pdfwrite \
   -dPDFACompatibilityPolicy=1 \
   -sOutputFile=output-pdfa3.pdf \
   input.pdf

libreoffice --headless --convert-to \
  "pdf:writer_pdf_Export:{\"SelectPdfVersion\":3}" \
  input.docx

How to validate PDF/A compliance

After conversion, verify that your PDF is actually valid PDF/A. Common validation tools:

• veraPDF (free, open-source): The reference PDF/A validator. Command-line and GUI versions available.
• Adobe Acrobat Preflight: Built-in PDF/A validation and correction.
• PDF/A Pilot (commercial): Batch validation and conversion.

# Validate with veraPDF
verapdf --flavour 3b output-pdfa3.pdf

# Expected output for valid PDF/A-3b:
# compliant: true

Frequently asked questions