The name of the person signing.
When you call the Sign
method, the name of the signer is automatically updated to match
the name associated with the private key.
Note that (while reading or validating a PDF file,) this
property can only be relied on if the certificate is valid. You can
check whether the certificate is valid using the Validate method.
You will not need to change the value of this property unless
you are writing low-level signature manipulation code.