Response.ContentType = "application/pdf";
Response.AddHeader("content-disposition", "attachment;filename=PurchaseOrderDetails.pdf");
Response.Cache.SetCacheability(HttpCacheability.NoCache);
StringWriter sw = new StringWriter();
HtmlTextWriter hw = new HtmlTextWriter(sw);
GridView gridview1 = new GridView();

gridview1.AllowPaging = false;
//DataSet ds = objOrderRegistratonController.GetOrders();
grddisplay.DataBind();
grddisplay.RenderControl(hw);
grddisplay.HeaderRow.Style.Add("width", "15%");
grddisplay.HeaderRow.Style.Add("font-size", "10px");
grddisplay.Style.Add("text-decoration", "none");
grddisplay.Style.Add("font-family", "Arial, Helvetica, sans-serif;");
grddisplay.Style.Add("font-size", "8px");
StringReader sr = new StringReader(sw.ToString());
Document pdfDoc = new Document(PageSize.A2, 7f, 7f, 7f, 0f);
HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
pdfDoc.Open();
htmlparser.Parse(sr);
pdfDoc.Close();
Response.Write(pdfDoc);
Response.End();