Represents the "Root" entry of the cross-reference stream dictionary object.

It is a required entry defined as part of the PDF 1.0 specification.

It contains a CatalogElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 17, page 50.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 17, page 65.

The Root entry in the cross-reference stream serves the same purpose as Root in the traditional trailer: it references the document catalog. Cross-reference streams subsume the trailer dictionary, so all trailer entries appear directly in the stream dictionary.