Like PDF digital signatures, XML digital signatures ensure integrity, authentication, and non-repudiation in documents.However, PDF signatures have multiple data verification states.When the form is complete, the agency certifies the document, allowing users to change only form fields and sign the document. However, if they remove pages or add comments, the document doesn’t retain its certified status.You can apply a certifying signature only if the PDF doesn’t already contain any other signatures. A blue ribbon icon in the Signatures panel indicates a valid certifying signature.Acrobat trusts all certificates for signing and certifying that chain up to a trust anchor.Therefore, administrators should preconfigure client installations or let their end users add a trust anchor or anchors.
XML data signatures conform to the W3C XML-Signature standard.
When you receive a signed document, you may want to validate its signature(s) to verify the signer and the signed content.
Depending on how you have configured your application, validation may occur automatically.
Some states are called when a user alters the PDF-signed content.
In contrast, XML signatures only have two data verification states, valid and invalid.