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?
You can read the vertices of an existing polygon annotations using the GetVertextCount and GetVertex methods.
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:
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.