A new version
1.9.32beta2
has been published, with a fix to annotation count issue.
To get the last created annotation, you can use
page.GetAnnot(page.AnnotCount - 1)
To export the annotations you need to save the info needed to recreate them like (page no, type, rectangle(position), fill color, stroke color,....)
Something like:
PDFAnnot mAnnot = page.GetAnnot(i);
PDFRect mRect = mAnnot.Rect;
int type = mAnnot.Type;
int fillColor = mAnnot.FillColor;
int srokeColor = mAnnot.StrokeColor;
if (type == 15) { //ink
PDFPath path = mAnnot.InkPath;
}