GridView tempGrd = new GridView();
tempGrd.DataSource = GridView1.DataSource;
tempGrd.DataBind();
Response.ContentType = "application/pdf";
Response.AddHeader("content-disposition","attachment;filename=DataTable.pdf");
//Response.Cache.SetCacheability(HttpCacheability.NoCache);
StringWriter sw = new StringWriter();
HtmlTextWriter hw = new HtmlTextWriter(sw);
tempGrd.RenderControl(hw); //We can't use GridView1 directly. This is the way to get the data...
StringReader sr = new StringReader(sw.ToString());
Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 10f, 0f);
HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
pdfDoc.Open();
htmlparser.Parse(sr);
pdfDoc.Close();
Response.Write(pdfDoc);
Response.End();