how to change font of pdf while Generating PDF from Html in C#.net

HtmlTextWriter w = new HtmlTextWriter(sw);
            //DivToPDF.RenderControl(w);
            TbltoPDF.RenderControl(w);
            string s = sw.GetStringBuilder().ToString();
            // string ins = "font-family:Zurich BT;font-size:8px;";
            s = s.Replace("font-size:11px;", "font-size:9px;");
            s = s.Replace("<table><tbody><tr><td>", "<table><tbody><tr><td style=" + ">");
            MemoryStream stream = new MemoryStream();
            PdfWriter.GetInstance(doc, stream);
            StringReader sr = new StringReader(s);
 iTextSharp.text.html.simpleparser.StyleSheet styles = new iTextSharp.text.html.simpleparser.StyleSheet();
            // Open the Document for writing
            doc.Open();           
ArrayList parsed = iTextSharp.text.html.simpleparser.HTMLWorker.ParseToList(sr, styles);
            for (int k = 0; k < parsed.Count; k++)
            {
                doc.Add((IElement)parsed[k]);
            }
            doc.Close();
           /// Byte[] buffer = stream.GetBuffer(); 

            Response.ContentType = "application/pdf";
            Response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}.pdf", Session["UserName"].ToString()));
           // Response.AddHeader("content-length", buffer.Length.ToString());
            Response.BinaryWrite(stream.ToArray());</td></tr></tbody></table></td></tr></tbody></table>