def gen_file_name(output_path, title):
    """Generates the name of the PDF-file from the "doc title" in the json file.
    Args:
        output_path (string): relative output path 
        title (string): title of the file according to content.json 
    Returns:
        string: file_name of the pdf-file
    """
    file_name = output_path + title + ".pdf"
    return file_name