how to add text in pdf programatically ?

Question

i have writter a code to export pdf from a gridview and its working fine i had total 39 columns in gridview in that i needed few columns so i hided rest of the unwanted columns from the grid.

 

its exporting pdf but i wanted to add some text in that pdf but i dont knw how to below is my code.

 

i want to add some text as disclaimer fixed text. 

 

public void exportPDFfile()
       {
           Response.ContentType = "application/pdf";
           Response.AddHeader("content-disposition", "attachment;filename=ForwardingLetter.pdf");
           Response.Cache.SetCacheability(HttpCacheability.NoCache);
           StringWriter sw = new StringWriter();
           HtmlTextWriter hw = new HtmlTextWriter(sw);

           //hide the link button column
           gridallemploye.Columns[0].Visible = false;
           gridallemploye.Columns[2].Visible = false;

           gridallemploye.Columns[3].Visible = false;
           gridallemploye.Columns[4].Visible = false;
           gridallemploye.Columns[5].Visible = false;
           gridallemploye.Columns[6].Visible = false;
           gridallemploye.Columns[7].Visible = false;
           gridallemploye.Columns[8].Visible = false;
           gridallemploye.Columns[9].Visible = false;

           gridallemploye.Columns[11].Visible = false;
           gridallemploye.Columns[12].Visible = false;
           gridallemploye.Columns[13].Visible = false;
           gridallemploye.Columns[14].Visible = false;
           gridallemploye.Columns[15].Visible = false;
           gridallemploye.Columns[16].Visible = false;
           gridallemploye.Columns[17].Visible = false;
           gridallemploye.Columns[18].Visible = false;
           gridallemploye.Columns[19].Visible = false;
           gridallemploye.Columns[20].Visible = false;
           gridallemploye.Columns[21].Visible = false;
           gridallemploye.Columns[22].Visible = false;
           gridallemploye.Columns[23].Visible = false;
           gridallemploye.Columns[24].Visible = false;
           gridallemploye.Columns[25].Visible = false;
           gridallemploye.Columns[26].Visible = false;
           gridallemploye.Columns[27].Visible = false;
           gridallemploye.Columns[28].Visible = false;
           gridallemploye.Columns[29].Visible = false;

           gridallemploye.Columns[30].Visible = false;
           gridallemploye.Columns[31].Visible = false;
           gridallemploye.Columns[32].Visible = false;
           gridallemploye.Columns[33].Visible = false;
           gridallemploye.Columns[34].Visible = false;


           gridallemploye.Columns[38].Visible = false;


           //Outputs server control content to a provided System.Web.UI.HtmlTextWriter
           gridallemploye.RenderControl(hw);

           //load the html content to the string reader
           StringReader sr = new StringReader(sw.ToString());

           //HTMLDocument
           //Document(Rectangle pageSize, float marginLeft, float marginRight, float marginTop, float marginBottom)
           Document document = new Document(PageSize.A4, 10f, 10f, 10f, 0f);

           //iText class that allows you to convert HTML to PDF
           HTMLWorker htmlWorker = new HTMLWorker(document);

           //When this PdfWriter is added to a certain PdfDocument,
           //the PDF representation of every Element added to this Document will be written to the outputstream.
           PdfWriter.GetInstance(document, Response.OutputStream);

           //open the document
           document.Open();

           htmlWorker.Parse(sr);

           //close the document stream
           document.Close();

           //write the content to the response stream
           Response.Write(document);
           Response.End();
       }