public function show_pdfAction($id)
{
    $em = $this->getDoctrine()->getManager();
    $mypdf = $em->getRepository('AppBundle:Article')->find($id);


    $pdfFile = stream_get_contents($mypdf->getArtPdf()); //returns pdf file stored as mysql blob
    $response = new Response($pdfFile, 200, array('Content-Type' => 'application/pdf'));