Represents the "MK" entry of the screen annotation object.

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

It contains an AppearanceCharacteristicsElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 187, page 407.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 190, page 494.

The appearance characteristics dictionary provides the visual appearance of the annotation region when no media is active, including border colour, background colour, and any icon or caption.