Adds a polygon annotation: the closed shape through vertices; its rectangle is fitted to them.
public PdfPolygonAnnotation AddPolygonAnnotation(IReadOnlyList<PathPoint> vertices, PdfAnnotationOptions? options = null)
At least three vertices in default user space.
Border and interior colours, width, flags and markup texts; null for a one-point red border.
ISO 32000-2 §12.5.6.9, Table 181 (PDF 1.5).