Represents the "SD" entry of the go-to action object.

It is an optional entry defined as part of the PDF 2.0 specification.

It contains a DestinationElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 199, page 418.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 202, page 508.

The SD entry is a string-keyed named destination, added to support arbitrary Unicode destination names in the string-keyed name tree alongside the byte-string-keyed tree addressed by D.