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

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 192, page 413.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 195, page 500.

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

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

A redaction annotation marks a region of a page for content removal. Creating the annotation is only the first step; the redaction is applied by a separate processing step that actually removes marked content.

The QuadPoints entry defines the regions to redact as quadrilaterals. The RO entry references a graphical overlay for the region before application. The OverlayText, Repeat, DA, and Q entries define the replacement text placed after content is removed.