Represents the "XRefStm" entry of the file trailer dictionary object.

It is an optional entry 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: 15, page 43.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 15, page 57.

The XRefStm entry gives the byte offset of a cross-reference stream in a hybrid-reference file. A hybrid file contains both a traditional cross-reference table and a cross-reference stream covering the same revision.

PDF 1.5 and later readers use the cross-reference stream for its compressed object references. PDF 1.4 and earlier readers use only the cross-reference table and ignore the stream. This allows a single file to be read by both old and new readers.