Represents the "Differences" entry of the fdf dictionary object.

It is an optional entry defined as part of the PDF 1.4 specification.

It contains a StreamElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 243, page 460.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 246, page 557.

The differences entry carries the cross-reference and resource information needed to apply incremental updates from the FDF to the target document.