public function removeWatermark($fileName)
    {
        //check whether files are set or not
        if ($fileName == '')
            throw new Exception('File not specified');

        //build URI to insert watermark image
        $strURI = Product::$baseProductUri . '/words/' . $fileName .
            '/watermark';

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

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

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

        if ($v_output === '') {
            //Save doc on server
            $folder = new Folder();
            $outputStream = $folder->GetFile($fileName);
            $outputPath = AsposeApp::$outPutLocation . $fileName;
            Utils::saveFile($outputStream, $outputPath);
            return $outputPath;
        } else
            return $v_output;
    }