When you digitally sign a document with a certificate-based signature, PSPDFKit Document Engine will use your configured signing service to calculate and apply a document-wide digital signature. As a result, PSPDFKit Document Engine will save the signed PDF as the new asset for the document. The old file is kept as the original asset for the document.
Your service tells PSPDFKit Document Engine to sign the document. The Document Engine retrieves the document from the asset storage.
Document Engine sends the digest of document content to the configured signing service. The signing service creates a signature by encrypting the digest using an asymmetric cryptography algorithm, and it then returns it to the Document Engine. The signing service can be the same service that made a signing request to the Document Engine.
PSPDFKit Document Engine embeds the signature in the document and saves the signed document in the asset storage, preserving the original. The information about the newly created signature is returned to the Document Engine.