Represents the "Pg" entry of the structure element dictionary object.

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

It contains a PageObjectElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 323, page 558.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 355, page 721.

The Pg entry references the page on which this element content primarily resides. It serves as the default page for child marked content references that do not specify their own Pg.