/// <summary>

         /// 添加倾斜水印

         /// </summary>

         /// <param name="pdfStream">pdf文件流</param>

         /// <param name="waterMarkName">水印字符串</param>

         /// <param name="width">页面宽度</param>

         /// <param name="height">页面高度</param>

         public MemoryStream SetWaterMark(MemoryStream pdfStream, string waterMarkName, float width, float height)

         {

             try

             {

                 int fontSize = ;//设置字体大小

                 int span = ;//设置垂直位移

                 MemoryStream outStream = new MemoryStream();

                 PdfReader pdfReader = new PdfReader(pdfStream);

                 PdfStamper pdfStamper = new PdfStamper(pdfReader, outStream);

                 pdfStamper.Writer.CloseStream = false;

                 int total = pdfReader.NumberOfPages + ;

                 PdfContentByte content;

                 BaseFont font = BaseFont.CreateFont(@"C:\WINDOWS\Fonts\STCAIYUN.TTF", BaseFont.IDENTITY_H, BaseFont.EMBEDDED);//华文云彩字体

                 PdfGState gs = new PdfGState();

                 gs.FillOpacity = 0.15f;//透明度

                 int waterMarkNameLenth = waterMarkName.Length;

                 char c;

                 int rise = ;

                 string spanString = " ";//水平位移

                 for (int i = ; i < total; i++)

                 {

                     rise = waterMarkNameLenth * span;

                     content = pdfStamper.GetOverContent(i);//在内容上方加水印

                                                            //content = pdfStamper.GetUnderContent(i);//在内容下方加水印

                     content.SetGState(gs);

                     content.BeginText();

                     content.SetColorFill(BaseColor.GREEN);

                     content.SetFontAndSize(font, fontSize);

                     int heightNumbert = (int)Math.Ceiling((decimal)height / (decimal)rise);//垂直重复的次数，进一发

                     int panleWith = (fontSize + span) * waterMarkNameLenth;

                     int widthNumber = (int)Math.Ceiling((decimal)width / (decimal)panleWith);//水平重复次数

                     // 设置水印文字字体倾斜 开始

                     for (int w = ; w < widthNumber; w++)

                     {

                         for (int h = ; h <= heightNumbert; h++)

                         {

                             int yleng = rise * h;

                             content.SetTextMatrix(w * panleWith, yleng);//x,y设置水印开始的绝对左边，以左下角为x，y轴的起点

                             for (int k = ; k < waterMarkNameLenth; k++)

                             {

                                 content.SetTextRise(yleng);//指定的y轴值处添加

                                 c = waterMarkName[k];

                                 content.ShowText(c + spanString);

                                 yleng -= span;

                             }

                         }

                     }

                     content.EndText();

                 }

                 if (pdfStamper != null)

                     pdfStamper.Close();

                 if (pdfReader != null)

                     pdfReader.Close();

                 return outStream;

             }

             catch (Exception ex)

             {

                 throw ex;

             }

         }