C#给PDF文件添加水印

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using iTextSharp.text.html.simpleparser;
using iTextSharp.text.pdf;
using iTextSharp.text;
using System.IO;
using System.Web.UI.HtmlControls;
using System.Drawing;

//itextsharp.dll version:5.1.10

protected void Button1_Click(object sender, EventArgs e)
  {
  string source =@"D:\My.Sample\C#NET\Exoport2PDF\Web2\Chap1011.pdf"; //模板路径
  string output = @"D:\My.Sample\C#NET\Exoport2PDF\Web2\Chap1012.pdf"; //导出水印背景后的PDF
  string watermark = @"D:\My.Sample\C#NET\Exoport2PDF\Web2\gp0.jpg"; // 水印图片

  bool isSurrcess = PDFWatermark(source, output, watermark, 10, 10);
  
  }


 public bool PDFWatermark(string inputfilepath, string outputfilepath, string ModelPicName, float top, float left)

 {
  //throw new NotImplementedException();
  PdfReader pdfReader = null;
  PdfStamper pdfStamper = null;
  try
  {
   pdfReader = new PdfReader(inputfilepath);

   int numberOfPages = pdfReader.NumberOfPages;

   iTextSharp.text.Rectangle psize = pdfReader.GetPageSize(1);

   float width = psize.Width;

   float height = psize.Height;

   pdfStamper = new PdfStamper(pdfReader, new FileStream(outputfilepath, FileMode.Create));

   PdfContentByte waterMarkContent;

   iTextSharp.text.Image image = iTextSharp.text.Image.GetInstance(ModelPicName);

   image.GrayFill = 20;//透明度，灰色填充
   //image.Rotation//旋转
   //image.RotationDegrees//旋转角度
   //水印的位置 
   if (left < 0)
   {
    left = width - image.Width + left;
   }

   image.SetAbsolutePosition(left, (height - image.Height) - top);


   //每一页加水印,也可以设置某一页加水印 
   for (int i = 1; i <= numberOfPages; i++)
   {
    waterMarkContent = pdfStamper.GetUnderContent(i);

    waterMarkContent.AddImage(image);
   }
   //strMsg = "success";
   return true;
  }
  catch (Exception ex)
  {
    ex.Message.Trim();
   return false;
  }
  finally
  {

   if (pdfStamper != null)
    pdfStamper.Close();

   if (pdfReader != null)
    pdfReader.Close();
  }