生成PDF并下载。

　　　　     　　//创建Document
            　　Document document = null;
            　　//为该Document创建一个Writer实例
            　　PdfWriter writer = null;
            　　//段（内容）
            　　Paragraph p = null;
　　　　　　　　　//字体
                BaseFont baseFont = BaseFont.CreateFont(Server.MapPath("Configuration/STZHONGS.TTF"), BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED);
                Font font = null;
                //内存流
                document = new Document(PageSize.A4.Rotate(), 90, 90, 40, 40);

                //为该Document创建一个Writer实例
                writer = PdfWriter.GetInstance(document, new FileStream(filepath + strCerId + ".pdf", FileMode.Create));
                //writer.SetEncryption(PdfWriter.STRENGTH40BITS, null, null, PdfWriter.ALLOW_PRINTING);
                //打开
                document.Open();

                //指定位置添加图片
                PdfContentByte pcb1 = writer.DirectContent;
                iTextSharp.text.Image image1 = iTextSharp.text.Image.GetInstance(Server.MapPath("Configuration/1.png"));
                image1.SetAbsolutePosition(62, 58);
                image1.ScaleAbsolute(724, 481);
                pcb1.AddImage(image1);

                font = new Font(baseFont, 18, Font.BOLD);
                p = new Paragraph("\n\n“标题", font);
                p.Alignment = Element.ALIGN_CENTER;
                document.Add(p);

                font = new Font(baseFont, 35, Font.BOLD);
                p = new Paragraph("标题", font);
                p.Alignment = Element.ALIGN_CENTER;
                document.Add(p);

                font = new Font(baseFont, 18, Font.NORMAL);
                p = new Paragraph("\n　　正文。", font);
                p.Alignment = Element.ALIGN_LEFT;
                document.Add(p);

                font = new Font(baseFont, 18, Font.NORMAL);
                p = new Paragraph("\n署名", font);
                p.Alignment = Element.ALIGN_RIGHT;
                document.Add(p);

                font = new Font(baseFont, 18, Font.NORMAL);
                p = new Paragraph("2016年6月22日", font);
                p.Alignment = Element.ALIGN_RIGHT;
                document.Add(p);

　　　　　　　　  //关闭目标文件
                document.Close();
                writer.Close();
                document = null;
                //关闭写入流  
                writer = null;