Use this method to extract the encoded X.509 data of the
certificate that was used to sign the document. Normally, there is
only one certificate returned, but for some documents, you may
receive additional certificates that can be used to create a
certificate chain. In such cases, the first certificate is always
the certificate that was used for signing.
You can pass the data returned by this function to the
X509Certificate2 class constructor in
System.Security.Cryptography.X509Certificates (in .NET BCL) and
then extract certificate details such as the subject, the issuer,
the serial number, the version, etc. See the Annotations example
project for details.