Represents the "ProcSet" entry of the resource dictionary
It is an optional entry defined as part of the PDF 1.0
specification. It was deprecated in PDF 2.0.
It contains an array which contains strings, representing PDF
For definitive details see:.
The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 33,
The ISO PDF
Specification, ISO 32000-2:2017 PDF 2.0; Table: 34, page 112.