I am trying to download pdf file of ID card with photo but not open the pdf its shoing error "failed to load PDF document."

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C#

HttpContext.Current.Response.Clear();
HttpContext.Current.Response.AddHeader
("Content-Disposition", "attachment;filename=iTextSharpExample.pdf");
HttpContext.Current.Response.Charset = "";
HttpContext.Current.Response.ContentType = "application/pdf";
StringWriter stringwrite = new StringWriter();
HtmlTextWriter htmlwrite = new HtmlTextWriter(stringwrite);
dvText.RenderControl(htmlwrite);
StringReader sr = new StringReader(stringwrite.ToString());
Document pdfDoc = new Document(PageSize.A4, 50, 50, 25, 25);
PdfWriter writer = PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
HTMLWorker htmlparser = new HTMLWorker(pdfDoc);

What I have tried:

I am trying to download pdf file of ID Card with photo but not open the pdf its shoing error "Failed to load PDF document."