Password-Protect a PDF — A Local, Private Guide
PDFMergeNext 目前专注于「合并、拆分、压缩、旋转、转图」这几件本地就能做好的事。加密/设置打开密码是另一类操作：浏览器纯前端目前难以在不引入重型依赖的情况下可靠地写入 PDF 加密。PDFMergeNext focuses on merge, split, compress, rotate, and PDF-to-image — all things the browser does well locally. Encryption (setting an open password) is a different job; doing it reliably in pure front-end code without heavy dependencies is still impractical.
但「隐私优先」的工作流里，密码保护很重要。下面讲清楚本地场景下你能怎么做，以及本工具已经帮到你哪里。But password protection still matters in a privacy-first workflow. Here is what you can do locally today, and where this tool already helps.
操作步骤 / How it works
1. 先用本地工具处理，最后再加密 / Process locally first, encrypt last
先用 PDFMergeNext 在本地完成合并/拆分/压缩，避免在多个在线工具间反复上传。Do your merge/split/compress locally here, so the file never travels to a server before it is locked.
2. 用你信任的本地软件设密码 / Set the password in software you trust
桌面端 PDF 阅读器（如本机安装的离线工具）可在本地给文件设打开密码；过程不联网更稳妥。A desktop PDF app you trust can set an open password entirely offline.
3. 带密码的 PDF 也能继续合并 / Encrypted PDFs still merge here
如果你有密码、用正确密码解密，PDFMergeNext 的合并流程可继续处理——解密也在本地。If you supply the correct password, our merge flow decrypts and processes it locally.
常见问题 / FAQ
PDFMergeNext 能直接给 PDF 设密码吗？
目前不能。浏览器纯前端可靠地写入 PDF 加密还不现实；我们把精力放在本地能做到极致的合并/拆分/压缩/旋转/转图上。Not yet — reliable in-browser PDF encryption isn’t practical today. We focus on what the browser does best locally.
那我的文件怎么保护？
先在本地完成所有处理（用本工具），最后用你信任的离线桌面软件设打开密码，全程不联网最稳妥。Process everything locally first, then set the open password in a trusted offline desktop app.
带密码的 PDF 能用本工具合并吗？
可以，前提是你知道密码并在本地正确解密；我们不会尝试破解任何密码。Yes, if you know the password and decrypt it locally — we never attempt to crack passwords.