Python拆分PDF、Python合并PDF

WPS能拆分合并，但却是要输入编辑密码，我没有。故写了个脚本来做拆分，顺便附上合并的代码。

代码如下（extract.py)

#!/usr/bin/env python
"""PDF拆分脚本(需要Python3.10+)

Usage::
    $ python extract.py <pdf-file>
"""
import os
import sys
from pathlib import Path

# pip install PyMuPDF
import fitz  # type:ignore[import-untyped]

SRC_FILE = Path.home() / "Downloads" / "yasi.pdf"


def new_one(pdf: fitz.Document, page_num: int, parent: Path | None = None) -> Path:
    target = Path(f"{page_num}.pdf")
    if parent is not None:
        target = parent / target.name
    new_pdf = fitz.Document()
    # 用第page_num页生成新的PDF文件
    index = page_num - 1
    new_pdf.insert_pdf(pdf, from_page=index, to_page=index)
    new_pdf.save(target)
    return target


def extract(
    file: Path,
    num: int | None = None,
) -> Path:
    """拆分PDF

    :param file: 文件路径
    :p