How to digitally sign PDF documents using .pfx certificates in UWP?

Stream inputStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("DigitalSignature.Assets.Barcode.pdf");
Stream certificateStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("DigitalSignature.Assets.PDF.pfx");
Stream imageStream = typeof(MainPage).GetTypeInfo().Assembly.GetManifestResourceStream("DigitalSignature.Assets.syncfusion_logo.gif");
 
//Loads a input pdf document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(inputStream);
 
//Gets the first page of the document.
PdfLoadedPage page = loadedDocument.Pages[0] as PdfLoadedPage;
 
//Creates a certificate instance from PFX file stream with private key.
PdfCertificate certificate = new PdfCertificate(certificateStream, "syncfusion");
 
//Creates a pdf signature using certificate..
PdfSignature signature = new PdfSignature(loadedDocument, page, certificate, "SignatureField");
signature.Bounds = new System.Drawing.RectangleF(50, 0, 100, 100);
PdfImage image = PdfImage.FromStream(imageStream);
page.Graphics.DrawImage(image, new System.Drawing.RectangleF(50, 0, 100, 100));
MemoryStream stream = new MemoryStream();
 
//Save the document in stream.
loadedDocument.Save(stream);
 
SaveFile(stream, "output.pdf");
//Close the document
loadedDocument.Close(true);