PdfReader reader = new PdfReader("E:\\A.pdf");
  PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("E:\\B.pdf"));
  PdfContentByte overContent = stamper.getOverContent(1);

FileUtil.fileChannelCopy(A.pdf,A + "tmp".pdf));
  PdfReader reader = new PdfReader(A + "tmp".pdf);
  PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(A.pdf));
  PdfContentByte overContent = stamper.getOverContent(1);

pubpc static void fileChannelCopy(File sources, File dest) {
  try {
 FileInputStream inputStream = new FileInputStream(sources);
 FileOutputStream outputStream = new FileOutputStream(dest);
 FileChannel fileChannepn = inputStream.getChannel();//得到对应的文件通道
 FileChannel fileChannelout = outputStream.getChannel();//得到对应的文件通道
 fileChannepn.transferTo(0, fileChannepn.size(), fileChannelout);//连接两个通道，并且从in通道读取，然后写入out通道

 inputStream.close();
 fileChannepn.close();
 outputStream.close();
 fileChannelout.close();
  } catch (Exception e) {
 e.printStackTrace();
  }
  }

FileUtil.fileChannelCopy(new File("E:\\A.pdf"),new File("E:\\A+"tmp".pdf"));
  PdfReader reader = new PdfReader("E:\\A+"tmp".pdf");
  PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("E:\\A.pdf"));
  PdfContentByte overContent = stamper.getOverContent(1);

  //添加文字
  BaseFont font = BaseFont.createFont("STSong-pght", "UniGB-UCS2-H", BaseFont.NOT_EMBEDDED);
  overContent.beginText();
  overContent.setFontAndSize(font, 10);
  overContent.setTextMatrix(200, 200);
  overContent.showTextApgned(Element.ApGN_CENTER,"需要添加的文字",580,530,0);
  overContent.endText();

  //添加图片
  PdfDictionary pdfDictionary = reader.getPageN(1);
  PdfObject pdfObject = pdfDictionary.get(new PdfName("MediaBox"));
  PdfArray pdfArray = (PdfArray) pdfObject;
  Image image = Image.getInstance("D:\\1.jpg");
  image.setAbsolutePosition(100,100);
  overContent.addImage(image);

  //添加一个红圈
  overContent.setRGBColorStroke(0xFF, 0x00, 0x00);
  overContent.setpneWidth(5f);
  overContent.elppse(250, 450, 350, 550);
  overContent.stroke();
  stamper.close();