def _get_pdfparam(self):
        """
        pdfparamオブジェクトを返す
        """
        pdfparam_path = os.path.abspath(
            os.path.join(self.work_dir, self._pdfparam_filename)
        )

        if "pdfparam" not in self._cache:
            if os.path.exists(pdfparam_path):
                mpac_data = bridge.load_msgpack(pdfparam_path)
                logger.debug("pdfparam({}) is loaded.".format(pdfparam_path))
                self._cache["pdfparam"] = pdf.PdfParam(mpac_data)
            else:
                pdfsim = pdf.PdfSim()
                self._cache["pdfparam"] = pdf.get_default_pdfparam()
                logger.debug("use default pdfparam.")
        else:
            logger.debug("pdfparam is cached.")

        return self._cache["pdfparam"]