question

Hi @QamarMo-8446,
From your description, I suggest that you can use jqu ery toDataURL to convert the canvas to image/png format first.
We can then use ajax to send this image to a web method in code-behind.
Finally, we can save the image in the web method.
You can refer to the demo below.
179506-behind.txt
179905-front.txt

Edit

  public static void UploadImage(string imageData)
         {          
             byte[] data = Convert.FromBase64String(imageData);
             Document pdfDoc = new Document();         
             var output = new FileStream(HttpContext.Current.Server.MapPath("2.pdf"), FileMode.Create);
             PdfWriter writer = PdfWriter.GetInstance(pdfDoc, output);
             pdfDoc.Open();
             iTextSharp.text.Image img = iTextSharp.text.Image.GetInstance(data);
              pdfDoc.Add(img);
              pdfDoc.Close();           
         }    
         protected void Button1_Click1(object sender, EventArgs e)
         {
             Process.Start(Server.MapPath("2.pdf"));
         }

Best regards,
Lan Huang

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