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.SampleC#NETExoport2PDFWeb2Chap1011.pdf"; //模板路径
    string output = @"D:My.SampleC#NETExoport2PDFWeb2Chap1012.pdf"; //导出水印背景后的PDF
    string watermark = @"D:My.SampleC#NETExoport2PDFWeb2gp0.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();
    }