Export gridview into PDF using asp.net c#

private void ExportGridToword()

    {

        DataTable dt = ViewState["dtt"] as DataTable;

        GridView gv = new GridView();

        gv.HeaderStyle.BackColor = System.Drawing.Color.Red;// System.Drawing.ColorTranslator.FromHtml("#DDDDDD");

        gv.HeaderStyle.ForeColor = System.Drawing.Color.LightGray;// System.Drawing.ColorTranslator.FromHtml("#CCCCCC");

        gv.RowStyle.BackColor = System.Drawing.Color.LightCyan;// System.Drawing.ColorTranslator.FromHtml("#454545");

        gv.AlternatingRowStyle.BackColor = System.Drawing.Color.White;// System.Drawing.ColorTranslator.FromHtml("#545454");

        gv.DataSource = dt;

        gv.DataBind();

        Response.ContentType = "application/pdf";

        Response.AddHeader("content-disposition", "attachment;filename=krishraja.pdf");

        Response.Cache.SetCacheability(HttpCacheability.NoCache);      

        StringWriter sw = new StringWriter();

        HtmlTextWriter hw = new HtmlTextWriter(sw);

        gv.RenderControl(hw);

        StringReader sr = new StringReader(sw.ToString());

        Document pdfDoc = new Document(PageSize.A2, 10f, 10f, 10f, 0f);

        HTMLWorker htmlparser = new HTMLWorker(pdfDoc);       

        PdfWriter.GetInstance(pdfDoc, Response.OutputStream);

        pdfDoc.Header = new HeaderFooter(new Phrase("Header Text"), false);

        pdfDoc.Open();

        htmlparser.Parse(sr);

        pdfDoc.Close();

        Response.Write(pdfDoc);

        Response.End();

    }