Represents the "Version" entry of the encrypted payload dictionary object.

It is an optional entry defined as part of the PDF 2.0 specification.

It contains a string representing a PDF name object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 28, page 94.

The Version entry records the PDF version of the encrypted payload document. A conforming reader may use this to determine whether it supports the version before attempting decryption.