title: Append full PDF file to FOP PDF
body: <p>I have an xml file already being created and rendered as a PDF sent over a servlet:</p>
  
  <pre><code>TraxInputHandler input = new TraxInputHandler(
     new File(XML_LOCATION+xmlFile+".xml"),
     new File(XSLT_LOCATION)
  );
  ByteArrayOutputStream out = new ByteArrayOutputStream();
  
  //driver is just `new Driver()`
  synchronized (driver) {
    driver.reset();
    driver.setRenderer(Driver.RENDER_PDF);
    driver.setOutputStream(out);
    input.run(driver);
  }
  
  //response is HttpServletResponse
  byte[] content = out.toByteArray();
  response.setContentType("application/pdf");
  response.setContentLength(content.length);
  response.getOutputStream().write(content);
  response.getOutputStream().flush();
  </code></pre>
  
  <p>This is all working perfectly fine.</p>
  
  <p>However, I now have another PDF file that I need to include in the output.  This is just a totally separate <code>.pdf</code> file that I was given.  Is there any way that I can append this file either to the response, the driver, <code>out</code>, or anything else to include it in the response to the client?  Will that even work?  Or is there something else I need to do?</p>