PdfWriter.GetInstance(document, new FileStream("Chap0404.pdf", FileMode.Create));
// step 3: we open the document
document.Open();
// step 4: we add a Graphic to the document
Graphic grx = new Graphic();
// add a rectangle
grx.Rectangle(100, 700, 100, 100);
// add the diagonal
grx.MoveTo(100, 700);
grx.LineTo(200, 800);
// stroke the lines
grx.Stroke();
document.Add(grx);