A circle annotation: an ellipse inscribed in the annotation rectangle (inset by RectangleDifferences).
public sealed class PdfCircleAnnotation : PdfMarkupAnnotation
ISO 32000-2 §12.5.6.8, Table 180 (PDF 1.3). The border is Border.
kind:method, kind:property, kind:ctor. Press Esc to clear.BorderEffectGets the border effect (BE, PDF 1.5), or null for none.InteriorColorGets or sets the interior colour (IC, PDF 1.4), or null for none; setting null removes it, and the appearance is kept until RegenerateAppearance().RectangleDifferencesGets the differences between the annotation rectangle and the drawn rectangle (RD, PDF 1.5), or null.