/**
  * creates a copy of the input file into the output file, and apply the given watermark at the center of all pages.
  * 
  * @param inputFile the path of the input document.
  * @param password the password of the input document.
  * @param outputFile the path of the output document.
  * @param watermarkPath the page to remove (0-based from 0 to GetPageCount() - 1)
  * @return true or false
  */
 public static boolean addWatermark(String inputFile, String password, String outputFile, String watermarkPath) {
     try {
         //init the library and activate the license
         Global.Init(company, email, key);
    
         //open the input file
         Document mInputFile = new Document();
         if(mInputFile.Open(inputFile, password) == 0) {
             //create the output file
             Document mOutputDoc = new Document();
             if(mOutputDoc.Create(outputFile) == 0) {
                 ImportContext mContext = mOutputDoc.ImportStart(mInputFile);
                 if(mContext != null) { //import all pages
                     int pagesCount = mInputFile.GetPageCount();
                     for(int i = 0; i < pagesCount; i++) 
                         mOutputDoc.ImportPage(mContext, i, i);
                     mContext.Destroy();
                 }
                 mOutputDoc.Save();
                 mOutputDoc.Close();
     
                 mOutputDoc.Open(outputFile, null);
                 addWatermark(mOutputDoc, watermarkPath);
             }
          }
          mInputFile.Close();
          return true;
      } catch (Exception e) {
          e.printStackTrace();
      }
      return false;
 }
 
 /**
  * Add a watermark to all the pages of the given document in the given position.
  * 
  * @param srcDoc the document to apply the watermark to.
  * @param watermarkPath the path of the watermark image.
  */ 
 public static void addWatermark(Document srcDoc, String watermarkPath) {
     try {
         BufferedImage bimg = ImageIO.read(new File(watermarkPath));
         int width = bimg.getWidth();
         int height = bimg.getHeight();
   
         DocImage dimg;  
         if(watermarkPath.toLowerCase().endsWith("png"))
             dimg = srcDoc.NewImage(bimg, true);
         else
             dimg = srcDoc.NewImageJPEG(watermarkPath);
         if(dimg != null) {
             for(int i = 0 ; i < srcDoc.GetPageCount() ; i++) {
                 Page page = srcDoc.GetPage(i);    
                 ResImage rimg = page.AddResImage(dimg);
                 if(rimg != null) {      
                     int watermarkX = (int) ((srcDoc.GetPageWidth(i) - width) / 2);
                     int watermarkY = (int) ((srcDoc.GetPageHeight(i) - height) / 2);
      
                     PageContent content = new PageContent();
                     content.Create();
                     content.GSSave();
                     Matrix mat = new Matrix( width, height, watermarkX, watermarkY);
                     content.GSSetMatrix(mat);
                     mat.Destroy();
                     content.DrawImage(rimg);
                     content.GSRestore();
                     //add content to page
                     page.AddContent(content, true);
                     content.Destroy();
                     page.Close();
                 }
             }
         }
     } catch (Exception e) {
         e.printStackTrace();
     }
     srcDoc.Save();
     srcDoc.Close();
 }