Mengapa penyesuaian font PDF saya menggunakan iTextSharp gagal?

Saya ingin menghias berbagai paragraf dalam file PDF dengan menebalkan beberapa teks, menggunakan font dan warna berbeda. Saya pikir saya menemukan kode untuk melakukan itu (di bawah), tetapi tidak berfungsi - semua teks memiliki font, warna (hitam), dan ukuran yang sama. Mengapa upaya virtual saya untuk mempercantik file PDF sejauh ini sia-sia? Ini kode saya:

using (var ms = new MemoryStream())
{

    using (var doc = new Document(PageSize.A4, 50, 50, 25, 25))
    {
        using (var writer = PdfWriter.GetInstance(doc, ms))
        {
            doc.Open();

            // Mimic the appearance of Duckbill_Platypus.pdf
            var docTitle = new Paragraph("Duckbilled Platypi - they're not what's for dinner");
            var titleFont = FontFactory.GetFont("Courier", 18, BaseColor.BLACK);
            docTitle.Font = titleFont;
            doc.Add(docTitle);

            var subTitle = new Paragraph("Baby, infant, toddler, and perhaps 'Terrible 2s' Platypi are called Platypups");
            var subtitleFont = FontFactory.GetFont("Times Roman", 13, BaseColor.BLACK);
            subTitle.Font = subtitleFont;
            doc.Add(subTitle);

            var importantNotice = new Paragraph("Teenage platypi are sometimes called Platydude[tte]s");
            var importantNoticeFont = FontFactory.GetFont("Courier", 13, BaseColor.RED);
            importantNotice.Font = importantNoticeFont;
            doc.Add(importantNotice);

            ListColumns lc;
            for (int i = 0; i < listOfListItems.Count; i++)
            {
                lc = listOfListItems[i];
                sb.AppendLine(String.Format(@"<p>Request date is {0}; Payee Name is {1}; Remit Address or Mail Stop is {2}; Last 4 of SSN or ITIN is {3}; 204 Submitted or on file is {4}; Requester Name is {5}; Dept or Div Name is {6}; Phone is {7}; Email is {8}</p>",
                    lc.li_requestDate, lc.li_payeeName, lc.li_remitAddressOrMailStop, lc.li_last4SSNDigitsOrITIN, lc.li_204SubmittedOrOnFile, lc.li_requesterName, lc.li_deptDivName, lc.li_phone, lc.li_email));
            }

            String htmlToRenderAsPDF = sb.ToString();

            //XMLWorker also reads from a TextReader and not directly from a string
            using (var srHtml = new StringReader(htmlToRenderAsPDF))
            {
                XMLWorkerHelper.GetInstance().ParseXHtml(writer, doc, srHtml);
            }

            doc.Close();
        }
    }
    try
    {
        var bytes = ms.ToArray();
        var testFile = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "iTextSharpTest.pdf");
        File.WriteAllBytes(testFile, bytes);
    }
    catch (Exception ex)
    {
        String exMsg = ex.Message;
        ; // what is "ex" here?
    }

Saya mengatur dua ukuran font (18 dan 13), dua warna (hitam dan merah), dua font ("Courier" dan "Times Roman") namun seluruh kerja keras saya di sini untuk fancification PDF tampaknya masih sia-sia (permintaan maaf kepada Vachel Lindsay dan Abraham Lincoln).