In some cases, however, the signature field becomes locked after you sign it.
If the signature status is unknown or unverified, validate the signature manually to determine the problem and possible solution.
Like PDF digital signatures, XML digital signatures ensure integrity, authentication, and non-repudiation in documents.
When certificate-based signatures are validated, an icon appears in the document message bar to indicate the signature status.
Additional status details appear in the Signatures panel and in the When you receive a signed document, you may want to validate its signature(s) to verify the signer and the signed content.
The form author provides XML signing, validating, or clearing instructions for form events, such as button click, file save, or submit.
XML data signatures conform to the W3C XML-Signature standard.
If the signature status is invalid, contact the signer about the problem.
For more information about signature warnings and valid and invalid signatures, see the Each time a document is signed using a certificate, a signed version of the PDF at that time is saved with the PDF.For more information on trusting certificates, see About digital signatures.You can add signatures to attachments before signing the cover sheet.To apply signatures to attached PDFs, open the PDF in a separate window.Right-click the attachment, and choose Open File from the context menu. To view an explanation of the problem, hover the pointer over a Signature Badge with a warning icon.Acrobat trusts all certificates for signing and certifying that chain up to a trust anchor.