PAdES (PDF Advanced Electronic Signature)

PAdES embeds an advanced electronic signature directly inside a PDF file.

Definition

PAdES (PDF Advanced Electronic Signature) is the advanced electronic signature profile designed for PDF documents. It builds on the PDF format's native signing mechanism (ISO 32000) while adding the attributes of an advanced signature.

The signature is embedded in the PDF: the file remains an ordinary PDF, readable by any viewer, yet becomes verifiable and tamper-evident.

How it works

PAdES stores the signature data in a signature dictionary inside the PDF, allowing a visible signature to be shown and guaranteeing document integrity.

Like other AdES profiles, it provides levels B, T, LT and LTA, together with PDF incremental updates, so timestamps and revocation data can be added without breaking existing signatures.

Good to know

PAdES is particularly suited to hybrid invoices such as Factur-X / ZUGFeRD, where a human-readable PDF/A-3 carries structured XML: the PAdES signature then covers the whole PDF container, including the embedded XML data.

Choosing between XAdES, CAdES and PAdES comes down to choosing the signed carrier: XML, a binary container, or a PDF.