public void iTextSharpCreatPDF()
        {
            string pdfpath = System.Web.HttpContext.Current.Server.MapPath("~/log/DPD/");
            string imagepath = System.Web.HttpContext.Current.Server.MapPath("~/log/DPD/");
            Document doc = new Document(new Rectangle(390, 400), 0, 0, 0, 0); //new Rectangle(1000,1000)
            //指定檔案預設開檔時的縮放為100%
            //PdfDestination pdfDest = new PdfDestination(PdfDestination.XYZ, 0, doc.PageSize.Height, 1f);
            try
            {
                PdfWriter.GetInstance(doc, new FileStream(pdfpath + "/DPD_15505984238198.pdf", FileMode.Create));
                doc.Open();

                //下面對圖片進行操作
                Image image = Image.GetInstance(imagepath + "/DPD_15505984238198.jpg");
                float percentage = 1;
                //這裡都是圖片最原始的寬度與高度
                float resizedWidht = image.Width;
                float resizedHeight = image.Height;

                ////這時判斷圖片寬度是否大於頁面寬度減去也邊距，如果是，那麼縮小，如果還大，繼續縮小，
                ////這樣這個縮小的百分比percentage會越來越小
                //while (resizedWidht > (doc.PageSize.Width - doc.LeftMargin - doc.RightMargin) * 0.8)
                //{
                //    percentage = percentage * 0.9f;
                //    resizedHeight = image.Height * percentage;
                //    resizedWidht = image.Width * percentage;
                //}
                ////There is a 0.8 here. If the height of the image is too close to the page size height,
                ////the image will seem so big
                //while (resizedHeight > (doc.PageSize.Height - doc.TopMargin - doc.BottomMargin) * 0.8)
                //{
                //    percentage = percentage * 0.9f;
                //    resizedHeight = image.Height * percentage;
                //    resizedWidht = image.Width * percentage;
                //}

                ////這裡用計算出來的百分比來縮小圖片
                image.ScalePercent(percentage * 100);
                //讓圖片的中心點與頁面的中心店進行重合
                image.SetAbsolutePosition(doc.PageSize.Width / 2 - resizedWidht / 2, doc.PageSize.Height / 2 - resizedHeight / 2);
                doc.Add(image);

            }
            catch (DocumentException dex)
            {
                System.Web.HttpContext.Current.Response.Write(dex.Message);
            }
            catch (IOException ioex)
            {
                System.Web.HttpContext.Current.Response.Write(ioex.Message);
            }

            catch (Exception ex)
            {
                System.Web.HttpContext.Current.Response.Write(ex.Message);
            }
            finally
            {
                doc.Close();
            }
        }