Represents the "Measure" entry of the line annotation object.

It is an optional entry defined as part of the PDF 1.7 specification.

It contains a MeasureElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 175, page 399.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 178, page 483.

The rectilinear measure dictionary maps the line's page-space length to a real-world measurement, allowing the annotation to display distances in physical units.