from pypdf import PdfReader, PdfWriter
from io import BytesIO

def 移除_pdf密碼(pdf檔案, 密碼):
    """
    解鎖帶有密碼保護的 PDF 檔案，回傳已解鎖的檔案（BytesIO）或錯誤訊息
    """
    try:
        reader = PdfReader(pdf檔案)
        if reader.is_encrypted:
            reader.decrypt(密碼)
        writer = PdfWriter()
        for page in reader.pages:
            writer.add_page(page)
        output = BytesIO()
        writer.write(output)
        output.seek(0)
        return output
    except Exception as e:
        return f"解鎖失敗：{e}"