title: TCPDF_import is not bringing in an existing file
body: <p>I have a PDF of a blank certificate, I want to fill in two lines when the user completes a course of study, and display the PDF so they can print or download it.</p>
  
  <p>I am using TCPDF to write the two lines on an existing PDF.</p>
  
  <p>Per suggestions in a previous post ( <a href="https://stackoverflow.com/questions/25837661/using-php-to-fill-in-a-pdf">using PHP to fill in a PDF</a> ), I am using TCPDF_IMPORT to bring an existing PDF into the object, and writing on top of it. </p>
  
  <p>However, the original PDF does NOT show on the screen, I am left with a blank document, with only the lines of text I created.</p>
  
  <p>Below is what I have to this point - it yields ONLY the line "This is my test text."</p>
  
  <pre><code>&lt;?php
  // Include the main TCPDF library (search for installation path).
  require_once( '../tcpdf_import.php' );
  
  // create new PDF document
  $pdf = new TCPDF_IMPORT( '1_cert.pdf' );
  
  // set document information
  $pdf-&gt;SetCreator( 'aaa.com' );
  $pdf-&gt;SetAuthor( 'aaa.com' );
  $pdf-&gt;SetTitle( 'Certificate Test' );
  $pdf-&gt;SetSubject( 'In completion of x-module' );
  $pdf-&gt;SetKeywords( '' );
  
  // set default monospaced font
  $pdf-&gt;SetDefaultMonospacedFont( PDF_FONT_MONOSPACED );
  
  // set font
  $pdf-&gt;SetFont( 'times', 'B', 30 );
  
  // display
  $pdf-&gt;SetDisplayMode( 'fullpage', 'SinglePage', 'UseNone' );
  
  // set margins
  $pdf-&gt;SetMargins( 10, PDF_MARGIN_TOP, 10 );
  
  // set auto page breaks
  $pdf-&gt;SetAutoPageBreak( TRUE, PDF_MARGIN_BOTTOM );
  
  // set image scale factor
  $pdf-&gt;setImageScale( PDF_IMAGE_SCALE_RATIO );
  
  // set some language-dependent strings (optional)
  if ( @file_exists( dirname( __FILE__ ).'/lang/eng.php' ) ) {
       require_once( dirname( __FILE__ ).'/lang/eng.php' );
       $pdf-&gt;setLanguageArray( $l );
  }
  
  
  // -------------------------------------------------------------
  // stuff i believe should write test over an existing PDF 
  // -------------------------------------------------------------
  
  $pdf-&gt;StartPage( 'L', '', false );
  $pdf-&gt;SetY( 50 );
  $pdf-&gt;Cell( 0, 0, 'test text', 0, 1, 'C' );
  $pdf-&gt;EndPage( false );
  
  // -------------------------------------------------------------
  // end of stuff i believe should write test over an existing PDF 
  // -------------------------------------------------------------
  
  //Close and output PDF document
  $pdf-&gt;Output( 'aTest.pdf', 'I' );
  ?&gt;
  </code></pre>