Q:

why courier font not working in iText PDF document? 

Using the following code to create a PDF document in C# using iText 5.  The text does not render in the courier font.  Why not? 
private void SimpleFontDoc(string pdfDocPath)
{
  Document doc = new Document(PageSize. LETTER, 10, 10, 42, 30);
  var fs = new FileStream(pdfDocPath, FileMode. Create);
  PdfWriter writer = PdfWriter. GetInstance(doc, fs);
  doc. Open();

  string[] lines = new string[]
    {
        "First   text   line",
        "Second  text   line"
    };
  var font = FontFactory. GetFont("courier", 12.0f, BaseColor. BLACK);

  foreach (var line in lines)
  {
    var para = new iTextSharp.text. Paragraph(line);
    para. Font = font;
    doc. Add(para);
  }

  doc. Close();
}

A:

In iText5 you have to specify the font before adding text to the Paragraph element (or alternatively pass it to the constructor). 
Change 
var para = new iTextSharp.text. Paragraph(line);
para. Font = font;

into
var para = new iTextSharp.text. Paragraph(line, font);

