Represents the "Type" entry of the page object object.
It is a required entry defined as part of the PDF 1.0
It contains a string representing a PDF name object.
This item must always be provided and must always take the value
For definitive details see:.
The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 30,
Adobe Supplement to the ISO 32000, BaseVersion: 1.7,
ExtensionLevel: 3; Table: 3.27, page 23.
The ISO PDF
Specification, ISO 32000-2:2017 PDF 2.0; Table: 31, page 103.