protected function addTokenToDocument(\Zend_Pdf $pdf, $tokenId, $surveyId)
    {
        $token = strtoupper($tokenId);

        foreach (array('Title', 'Subject', 'Keywords') as $name) {
            if (isset($pdf->properties[$name])) {
                $orgValue = $pdf->properties[$name];
                if (mb_detect_encoding($orgValue) === false) {
                    // Assume UTF-16
                    mb_convert_encoding($orgValue, mb_internal_encoding(), 'UTF-16');
                }
                $value = rtrim($orgValue) . ' ' . $token;
            } else {
                $value = $token;
            }
            $pdf->properties[$name] = $value;
        }
        // Acrobat defined date format D:YYYYMMDDHHmmSSOHH'mm
        $pdf->properties['ModDate']  = 'D:' . str_replace(':', "'", date('YmdHisP')) . "'";
        $pdf->properties['Producer'] = $this->project->getName();       // Avoid warning on Word with a (R) symbol
        $pdf->properties['Creator']  = $this->project->getName();       // Avoid warning on Word with a (R) symbol
        $pdf->properties['Author']   = $this->project->getName();       // Avoid warning on Word with a (R) symbol
    }