Add polygon annotation to the current page of the doc.
When you create this type of annotation the Annotation.Rect is
determined by the bounds of the vertices assuming a default border
width. If you change the border width or the cloudiness you need to
increase the size of the rectangle to accommodate the increase in
The size that is required is related to two factors - the border
width and the cloudiness factor. The extent related to the border
is equal to half the border width. The extent related to the
cloudiness is the cloudiness level (between zero and two)
multiplied by four. At creation the default border is one pixel so
the Annotation.Rect extends out by 0.5 points from the bounds of
Note that this is different from the way width and cloudiness
are handled in the SquareAnnotation and
For these the Annotation.Rect defines the bounds of the shape
rather than the shape itself - so in this situation the clouds lie
inside the bounds rather than extending out from the vertices.