Thanks for the additional information.
Just to clarify, currently you have a number or coordinates from your app that always reference the origin as the bottom left of the page as shown in the viewer, no matter the rotation. Now you would like to use these page coordinates to add annotations to the page using PDFTron API. Is that correct?
If this is the case, there are a number of solutions:
Solution 1. You will need to calculate the proper page coordinates (to be used with PDFTron API) from your existing coordinates. For example you will need to determine the rotation of the page, calculate the bounding box for the annotation, and then set the rotation of the annotation.
Also, as mentioned previously: Can i get fixed PDF page co-ordinates (Bottom-left point ) irrespective of Pdf page rotation? - #4 by Ryan , the GetDefaultMatrix API may be helpful in this case.
Solution 2. A simpler solution would be to create an XFDF using your current PDF library and import the XFDF using the PDFTron API. We suggest going with this option if possible.
If this is not what you’re looking for, would it be possible if you could send us a concrete example? For example some detailed steps to recreate your flow with a sample PDF, example page points, sample code, etc…? If possible, a sample project would also be very helpful.