This class represents the caret annotation. This is definitively detailed in:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 180, page 404.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 183, page 489.

This class is always an indirect object because it inherits from MarkupAnnotationElement which is always an indirect object.

System.Object
    WebSupergoo.ABCpdf14.Elements.Element
       WebSupergoo.ABCpdf14.Elements.AnnotationElement
          WebSupergoo.ABCpdf14.Elements.MarkupAnnotationElement
             WebSupergoo.ABCpdf14.Elements.CaretAnnotationElement

A caret annotation places a symbol at a point in text to indicate an insertion position. The Sy entry selects the symbol: a plain caret or a paragraph mark. The RD entry insets the drawn area from the annotation's Rect.