public function getDocumentProperties()
    {

        //build URI to replace image
        $strURI = Product::$baseProductUri . '/pdf/' . $this->getFileName() . '/documentProperties';

        //sign URI
        $signedURI = Utils::sign($strURI);
        $responseStream = Utils::processCommand($signedURI, 'GET', '', '');

        $response_arr = json_decode($responseStream);

        return $response_arr->DocumentProperties->List;
    }