pdf generation and downloading at button click event

Question

can you please help me to generate and download pdf document on buton click event

 

below code is giving error as path is not legal formate

protected void btnGenerateCertificate_Click(object sender, System.EventArgs e)
{
string imageURL = Server.MapPath("../images/logo.png");
iTextSharp.text.Image jpg = iTextSharp.text.Image.GetInstance(imageURL);

//Resize image depend upon your need
jpg.ScaleToFit(25f, 25f);
//Give space before image
//jpg.SpacingBefore = 1f;
//Give some space after the image
jpg.SpacingAfter = 1f;
jpg.Alignment = Element.ALIGN_CENTER;

//Header
Paragraph parag = new Paragraph("Road Construction Department", new iTextSharp.text.Font(iTextSharp.text.Font.FontFamily.TIMES_ROMAN, 15f, iTextSharp.text.Font.BOLD, iTextSharp.text.BaseColor.BLUE));
Paragraph paradate;
Paragraph subparag;
parag.SpacingAfter = 1f;
parag.Alignment = Element.ALIGN_CENTER;

subparag = new Paragraph("Govt. of Jharkhand", new iTextSharp.text.Font(iTextSharp.text.Font.FontFamily.TIMES_ROMAN, 15f, iTextSharp.text.Font.BOLD, iTextSharp.text.BaseColor.BLACK));
//subparag.SpacingAfter = 1f;
subparag.Alignment = Element.ALIGN_CENTER;
string AppId = Session["ApplicantId"].ToString();
string datetime = DateTime.Now.ToString("dd-MMM-yyyy-H-mm-ss");
string filename = "Certificate_" + Session["ApplicantId"].ToString() + "_" + datetime + ".pdf";
FileStream file = new FileStream(Server.MapPath("~/Certificate/") + filename, FileMode.Create, System.IO.FileAccess.Write);
//save filename in database
string param = AppId + "~" + filename;
DataSet ds = BLobj.contractor_registration_Insert_Update_Certificate(connString, param);
StringWriter sw = new StringWriter();
HtmlTextWriter hw = new HtmlTextWriter(sw);
printableArea_IA_IB_IS.RenderControl(hw);
StringReader sr = new StringReader(sw.ToString());
Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 100f, 0f);
PdfWriter.GetInstance(pdfDoc, file);
pdfDoc.Open();
pdfDoc.Add(jpg);
pdfDoc.Add(parag);
pdfDoc.Add(subparag);
HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
MemoryStream ms = new MemoryStream();
htmlparser.Parse(sr);
pdfDoc.Close();
file.Close();
Response.Redirect("Summary_Application1.aspx");
}