Legally the signing event itself carries weight – not the image on the page. But in practice the stamp is still required: courts demand it when admitting documents to a case, counterparties keep it for paper archives and tax inspections, and procurement portals use it as proof of submission. Without the imprint a printed PDF looks like an ordinary printout that shows no sign of being signed.
Upload the signed PDF together with the signature file (.sig, .p7s, or .p7b – both CMS/PKCS#7 and Russian GOST signatures are supported). The service parses the certificate and pulls out the holder's name, taxpayer/insurance/role identifiers (when present), serial number, validity dates, and the issuing authority. It then generates a stamp with those details and overlays it on the chosen page – first page by default. The PDF stays cryptographically valid: the stamp is a visual layer and does not break signature integrity.
A few practical notes. If a package carries several signatures (for example, director and chief accountant), run the file once per .sig so both stamps land on the page. If the signature is detached, upload both the original PDF and the .sig file – without the signature the service cannot extract the details. And for archival storage it is worth keeping the original .sig alongside the stamped PDF: in a dispute, the legal argument is the cryptography, not the picture.