Q:
I have a document containing polygon annotations (which are used to “highlight” parts of blueprints for measurement tools). How can I find the vertices covered by that annotation?
A:
You can read the vertices of an existing polygon annotations using the GetVertextCount and GetVertex methods.
https://www.pdftron.com/pdfnet/docs/PDFNet/html/M_pdftron_PDF_Annots_PolyLine_GetVertex.htm
https://www.pdftron.com/pdfnet/docs/PDFNet/html/M_pdftron_PDF_Annots_PolyLine_GetVertexCount.htm
You can obtain the bounding box of the annotation using GetRect: https://www.pdftron.com/pdfnet/docs/PDFNet/html/M_pdftron_PDF_Annot_GetRect.htm
The following describes how to obtain the page coordinates of paths within a PDF page:
https://groups.google.com/d/msg/pdfnet-sdk/AZAWD3-lC_4/S3DBG-guIp0J
You can also use ElementReader (https://www.pdftron.com/pdfnet/samplecode.html#ElementReader) to find the path elements, and use getBBox to find the bounding box of each.