PAdES uses ETSI.CAdES.detached CMS signatures with signed attributes such as the signing certificate reference. B-T adds a signature timestamp; B-LT adds a Document Security Store (DSS) with certificates, CRLs and OCSP responses needed to validate later; B-LTA adds document timestamps that can be renewed before algorithms weaken, keeping signatures verifiable for decades.
It is the standard format for qualified electronic signatures on PDFs in the EU, and validators such as the European Commission's DSS library check it against EU trusted lists. Similar profiles exist for XML (XAdES), CMS (CAdES) and containers (ASiC).