Represents the "V" entry of the encryption dictionary object.

It is defined as part of the PDF 1.0 specification.

It contains an integer representing a PDF numeric object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 20, page 56.

Adobe Supplement to the ISO 32000, BaseVersion: 1.7, ExtensionLevel: 3; Table: 3.18, page 14.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 20, page 72.

The V entry selects the encryption algorithm. V 1 uses 40-bit RC4. V 2 uses variable-length RC4 (40 to 128 bits). V 3 is unpublished. V 4 introduces crypt filters and AES-128. V 6, defined in PDF 2.0, uses AES-256 with a revised key derivation algorithm.

Higher V values require higher PDF versions. V 6 requires PDF 2.0 and the revision 6 standard security handler.