@staticmethod
def __add_filename_suffix(filename, suffix):
    """
        Add a suffix to a filename (before the extension).
        The suffix is extracted from the config file.
        :param filename: filename to add the suffix to
        :param suffix: suffix given to the compressed file (before the extension)
        :return: filename with suffix appended
        """
    return '{}{}.pdf'.format(filename.split('.pdf', 1)[0], suffix)
