Represents the "Contents" entry of the annotation dictionary object.

It is an optional entry defined as part of the PDF 1.0 specification.

It contains a string representing a PDF string object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 164, page 383.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 166, page 464.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 252, page 467.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 255, page 565.

The contents string is used differently by different annotation types. For text-bearing annotations it holds the main annotation text shown in a pop-up. For non-text annotations it may serve as an alternate text description for accessibility.