PAdES: PDF Signature Profiles and Evidence

What is PAdES?

PAdES stands for PDF Advanced Electronic Signatures. It specifies structures and requirements for digital signatures within PDF, rather than the appearance of a signature image. The word “Advanced” in the name does not automatically establish the legal conditions for AES or QES in a particular transaction.

ETSI EN 319 142-1 defines PAdES building blocks and baseline signatures. The profile identifies a technical set of requirements, not a universal judgment that a contract is legally enforceable.

B-B, B-T, B-LT and B-LTA

• PAdES B-B: meets the baseline’s basic signature requirements.
• PAdES B-T: adds requirements supporting reliable evidence that the signature existed by a particular time.
• PAdES B-LT: incorporates validation material, including relevant certificates and revocation information.
• PAdES B-LTA: adds protection of long-term availability and integrity through document timestamp mechanisms, supporting subsequent preservation.

The levels build on lower requirements. Higher evidence content does not mean the signer had greater company authority or that every statement in the PDF is true. B-LTA can require continuing preservation or renewal measures; it does not mean “valid forever.”

Profile versus legal qualification

A timestamp and embedded validation data can support later validation. Qualified-signature status depends on additional certificate, creation and service requirements, including applicable qualified-service information. It should not be inferred from a profile label alone.

PAdES versus PDF/A and containers

PDF/A concerns a preservation-oriented PDF format. PAdES concerns signatures and evidence within PDF. An ASiC package provides another way of associating files with signatures or time assertions; it is not simply another name for a PAdES PDF.

These distinctions belong to the wider signature-format landscape. For practical checks on a received file, the existing electronic-signature verification guide covers the review process.