PAdES

PAdES (EN 319 142) is the ETSI standard for embedding electronic signatures and seals inside PDF documents, keeping the file self-contained.

PAdES (PDF Advanced Electronic Signatures) is the ETSI standard (EN 319 142) that defines how an electronic signature or electronic seal is embedded inside a PDF document. It builds on the native digital signature feature of the ISO 32000 PDF standard, using the same CMS-based cryptography as CAdES, but keeps the signature inside the PDF's own signature dictionary rather than as a separate file - so the signed document stays a single, self-contained PDF that any standard PDF reader can open.

Like the other AdES signature formats, PAdES defines baseline profiles that add increasing levels of evidence: B-B (the basic signature), B-T (adds a qualified timestamp), B-LT (adds certificate and revocation data for long-term validation) and B-LTA (adds periodic re-timestamping to remain verifiable for decades). Because PDF is the default format for contracts, invoices and official documents, PAdES is the most commonly used AdES format for qualified electronic signatures and seals in practice.