Certificate-based signatures, Certifying and signing documents, Certificate – Adobe Acrobat XI User Manual
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Electronic signatures
Last updated 1/14/2015
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Certificate-based signatures
A certificate-based signature, like a conventional handwritten signature, identifies the person signing a document.
Unlike a handwritten signature, a certificate-based signature is difficult to forge because it contains encrypted
information that is unique to the signer. It can be easily verified and informs recipients whether the document was
modified after the signer initially signed the document.
To sign a document with a certificate-based signature, you must obtain a digital ID or create a self-signed digital ID in
Acrobat or Adobe Reader. The digital ID contains a private key and a certificate with a public key and more. The private
key is used to create the certificate-based signature. The certificate is a credential that is automatically applied to the
signed document. The signature is verified when recipients open the document.
When you apply a certificate-based signature, Acrobat uses a hashing algorithm to generate a message digest, which it
encrypts using your private key. Acrobat embeds the encrypted message digest in the PDF, certificate details, signature
image, and a version of the document when it was signed.
Certifying and signing documents
The Sign > Work with Certificates panel lets you apply two types of certificate-based signatures. You can certify a
document attest to its content or approve a document with the Sign With Certificate option.
Certify
Certify options provide a higher level of document control than Sign With Certificate. For documents that
require certification, you must certify the documents before others sign them. If a document has already been signed,
the Certify options are disabled. When you certify a document, you can control the types of changes other people can
make. You can certify with or without displaying a signature.
Sign With Certificate
When you sign with a certificate, the signature is considered an approval signature.