how to export web page in pdf

Quote:

the error id: input string was not in correct format.

protected void btn_print_Click(object sender, EventArgs e)
{

    Response.ContentType = "application/pdf";
    Response.AddHeader("content-disposition", "attachment;filename=UserDetails.pdf");
    Response.Cache.SetCacheability(HttpCacheability.NoCache);
    StringWriter sw = new StringWriter();
    HtmlTextWriter hw = new HtmlTextWriter(sw);
    this.Page.RenderControl(hw);
    StringReader sr = new StringReader(sw.ToString());
    Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 100f, 0f);
    HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
    PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
    pdfDoc.Open();
    htmlparser.Parse(sr);
    pdfDoc.Close();
    Response.Write(pdfDoc);
    Response.End();

}

public override void VerifyRenderingInServerForm(Control control)
{
    /* Verifies that the control is rendered */
}