Hi,

Basically, the problem is not your code. It's the HTML that you are passing to iTextSharp. There is most likely something it doesn't lik in the HTML

check code in below

protected void btnExportPDF_Click(object sender, EventArgs e)
{
    Response.ContentType = "application/pdf";
    Response.AddHeader("content-disposition",
     "attachment;filename=GridViewExport.pdf");
    Response.Cache.SetCacheability(HttpCacheability.NoCache);
    StringWriter sw = new StringWriter();
    HtmlTextWriter hw = new HtmlTextWriter(sw);
    GridView1.AllowPaging = false;
    GridView1.DataBind();
    GridView1.RenderControl(hw);
    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();
}

Link

http://www.aspsnippets.com/Articles/Export-GridView-To-Word-Excel-PDF-CSV-Formats-in-ASP.Net.aspx

http://am22tech.com/s/22/Blogs/post/2011/09/28/HTML-To-PDF-using-iTextSharp.aspx