public function explode($pdf, array $pageRangesLength = array())
    {
        $pdf = $this->getPdfInstance($pdf);
        if (empty($pageRangesLength)) {
            $pageRangesLength = array_fill(0, $pdf->getPageCount(), 1);
        }
        $pdfs = array();
        $offset = 1;
        foreach ($pageRangesLength as $length) {
            $pdfs[] = $this->getRange($pdf, $offset, $length);
            $offset += $length;
        }
        return $pdfs;
    }