c给PDF所有页加上文字水印

　　给一个PDF的所有页加上文字水印，效果如下
　　新建一个项目，直接上代码了：using iTextSharp.text; using iTextSharp.text.pdf; using System; using System.IO; using System.Windows.Forms;  namespace _111 {     public partial class Form1 : Form     {         public Form1()         {             InitializeComponent();         }          private void button1_Click(object sender, EventArgs e)         {             string p = Application.StartupPath + ＂＂;             string r = AddTextShuiYin(p + ＂test.pdf＂, p + ＂test1.pdf＂, 0.5f,  ＂HELLO＂);              MessageBox.Show(r);         }         public static string AddTextShuiYin(string PdfPath, string OutPdfPath, float toumingdu, string ShuiYinText)         {             if (File.Exists(OutPdfPath))             {                 File.Delete(OutPdfPath);             }              PdfReader reader = null;             PdfStamper ShuiYinOBJ = null;             PdfContentByte ShuiYinQu;             try             {                 reader = new PdfReader(PdfPath);                  //得到原PDF的页数和宽高                 PDFATT att = new PDFATT(PdfPath);                 int n = att.PageCount();                 float w = att.Width();                 float h = att.Height();                  //从第0页开始                 int i = 0;                  ShuiYinOBJ = new PdfStamper(reader, new FileStream(OutPdfPath, FileMode.Create));                 PdfGState gs = new PdfGState();                 //设置透明度                 gs.FillOpacity = toumingdu;                  BaseFont font = BaseFont.CreateFont(@＂C:WINDOWSFontsSIMFANG.TTF＂, BaseFont.IDENTITY_H, BaseFont.EMBEDDED);                 while (i < n)                 {                     i++;                      //在正文内容下加水印，不挡内容                     ShuiYinQu = ShuiYinOBJ.GetUnderContent(i);                      //在正文内容上加水印，挡内容                     //ShuiYinQu = ShuiYinOBJ.GetOverContent(i);                     ShuiYinQu.SetGState(gs);                      for (float left = 0; left < w; left += 200)                     {                         for (float top = 0; top < h; top += 100)                         {                             //透明度                             gs.FillOpacity = toumingdu;                             ShuiYinQu.SetGState(gs);                              //开始写入文本                             ShuiYinQu.BeginText();                             ShuiYinQu.SetColorFill(iTextSharp.text.Color.RED);                             ShuiYinQu.SetFontAndSize(font, 180);                             ShuiYinQu.SetTextMatrix(2, 2);                              ShuiYinQu.ShowTextAligned(Element.ALIGN_CENTER, ShuiYinText, w / 2, h / 2, 30);                             //ShuiYinQu.AddImage(im);                         }                     }                     ShuiYinQu.EndText();                 }                  ShuiYinOBJ.Close();                 reader.Close();                  return ＂OK＂;             }             catch (Exception ex)             {                 return ex.ToString();              }         }         class PDFATT         {             PdfReader reader;             public PDFATT(string iPdfFilePath)             {                 reader = new PdfReader(iPdfFilePath);             }             public int PageCount()             {                 return reader.NumberOfPages;             }             public float Width()             {                 return reader.GetPageSize(1).Width;             }             public float Height()             {                 return reader.GetPageSize(1).Height;             }         }     } }调用方法说明
　　string p = Application.StartupPath + ＂＂;
　　//参数：源文件地址，新文件地址，透明度(float型),水印文本
　　string r = AddTextShuiYin(p + ＂test.pdf＂, p + ＂test1.pdf＂, 0.5f, ＂HELLO＂);
　　MessageBox.Show(r);水印位置
　　//这里我是w/2和h/2，大概在页中间，当然这里我为了演示没有精确计算，
　　//30 是旋转角度
　　ShuiYinQu.ShowTextAligned(Element.ALIGN_CENTER, ShuiYinText, w / 2, h / 2, 30);下次研究下加图片水印