Represents the "Name" entry of the signature dictionary object.

It is an optional entry defined as part of the PDF 1.0 specification.

It contains a string representing a PDF string object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 252, page 468.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 255, page 566.

The signer name string identifies who signed the document. It is human-readable text distinct from the certificate subject name and may be a display name or organisational role.