Merge existing annotation to .png file

I am using PDFTron sdk. I have .png file and annotations in separate server.
I want merge existing annotations to .png file. I can merge annotations to file using following code,

pdftron.PDF.Convert.ToPdf(pdfdoc, @"C:\TestFiles\apple.png");
                var fdfdoc = new FDFDoc(
pdfdoc.Save(@"C:\OutputFiles\the_rime_of_the_ancient_mariner2.pdf", SDFDoc.SaveOptions.e_compatibility);

But my problem is, .png actual size(widht:114px, height:114px), in pdftron web viewer image enlarged upto width:797px, height:800px, on that we did some annotations.

By using above code, final output is not matching with pdftron webviewer annotations. How to make it same like pdftron webviewer annotations. Please let me is there any other way to merge annotations to .png using c# PDFTron SDK.

Arun Kumar

​Can you provide the apple.png, or any png, that triggers this issue?

Also it sounds like you are loading the PNG into WebViewer. If you call Document.getFileData() client side, you can get the annotated PDF from WebViewer.