public function getAttachment($attachmentIndex)
    {

        $strURI = Product::$baseProductUri . '/pdf/' . $this->getFileName() . '/attachments/' . $attachmentIndex;
        $signedURI = Utils::sign($strURI);
        $responseStream = Utils::processCommand($signedURI, 'GET', '', '');
        $json = json_decode($responseStream);
        return $json->Attachment;
    }