public function convert($folder = null)
    {
        //build URI
        $strURI = Product::$baseProductUri . '/words/' . $this->getFileName() . '?format=' . $this->saveFormat;
        if ($folder) {
            $strURI = $strURI . "&folder=" . urlencode($folder);
        }

        //sign URI
        $signedURI = Utils::sign($strURI);

        $responseStream = Utils::processCommand($signedURI, 'GET', '', '');

        $v_output = Utils::validateOutput($responseStream);

        if ($v_output === '') {
            if ($this->saveFormat == 'html') {
                $save_format = 'zip';
            } else {
                $save_format = $this->saveFormat;
            }
            $outputPath = AsposeApp::$outPutLocation . Utils::getFileName($this->getFileName()) . '.' . $save_format;
            Utils::saveFile($responseStream, $outputPath);
            return $outputPath;
        } else {
            return $v_output;
        }
    }