/**
  * Merges the given 2 files into the output file, (first file followed by the second one) 
  * 
  * @param firstFile the path of the first document.
  * @param firstPwd the password of the first document.
  * @param secondFile the path of the second document.
  * @param secondPwd the password of the second document.
  * @param outputFile the path of the output document.
  * @return true or false
  */
 public static boolean mergePDF(String firstFile, String firstPwd, String secondFile, String secondPwd, String outputFile) {
     try { 
         //init the library and activate the license
         Global.Init(company, email, key);
   
         //create the output file
         Document mOutputDoc = new Document();
         if(mOutputDoc.Create(outputFile) == 0) {
             int destno = 0;
             //import the first file
             Document mInputFile = new Document();
             if(mInputFile.Open(firstFile, firstPwd) == 0) {    
                 ImportContext mContext = mOutputDoc.ImportStart(mInputFile);
                 if(mContext != null) { //import all pages
                     int pagesCount = destno = mInputFile.GetPageCount();
                     for(int i = 0; i < pagesCount; i++) 
                         mOutputDoc.ImportPage(mContext, i, i);
                     mContext.Destroy();
                 }
     
              }
              mInputFile.Close();
    
              //import the second file
              mInputFile = new Document();
              if(mInputFile.Open(secondFile, secondPwd) == 0) {    
                  ImportContext mContext = mOutputDoc.ImportStart(mInputFile);
                  if(mContext != null) { //import all pages
                      int pagesCount = mInputFile.GetPageCount();
                      for(int i = 0; i < pagesCount; i++, destno++) 
                          mOutputDoc.ImportPage(mContext, i, destno);
                   mContext.Destroy();
                   }     
              }
              mInputFile.Close();
        }
        mOutputDoc.Save();
        mOutputDoc.Close();
        return true;
    } catch (Exception e) {
       e.printStackTrace();
    }
    return false;
 }