保护 PDF
免费·无需注册·文件永不离开你的设备
How to password-protect a PDF in 3 steps
Real encryption, applied in your browser: a password to open, and permissions that travel with the file.
Upload the PDF
Drop the document in the box above. Encryption happens locally — even the password stays on your device.
Set password and rules
Choose the open password, then optionally restrict printing, copying, or editing.
Download the locked file
Click Protect. The encrypted PDF downloads immediately, ready to share safely.
Why protect PDFs with AmiPDF
Standard PDF encryption without handing the document to a server.
隐私优先
处理完全在你的浏览器内完成。不上传、不存储、不外传——绝不。
无需注册，无水印
无账号、无邮箱、无限制。输出文件与输入完全一致。
Granular permissions
Beyond the open password, control whether recipients can print, copy text, or modify — enforced by every compliant PDF reader.
任何设备可用
Windows、Mac、Linux、Android、iOS 上体验一致——无需安装。
When to password-protect a PDF
Tax documents sent by email, legal drafts shared with counterparties, employee records passed between systems, exam papers distributed early. A password turns an open letter into a sealed envelope.
Encryption runs on your device — the unencrypted file and the password both stay local.
Password-protect PDFs on any platform
AmiPDF 在你的浏览器中运行——无需安装、无需配置、无需更新。
Windows
Chrome, Edge, Firefox
macOS
Safari, Chrome
Linux
Any modern browser
iOS
Safari on iPhone, iPad
Android
Chrome, Samsung Internet
Frequently asked questions
What encryption does AmiPDF use?
Standard PDF encryption (AES) — the same mechanism Acrobat and every mainstream reader support. Protected files open anywhere with the password.
What's the difference between the two passwords?
The open password is required just to view the file. The permissions password (optional) guards the restriction settings — recipients can read freely but need it to change permissions.
Can restrictions be bypassed?
Permissions are enforced by compliant readers, which covers the tools people actually use. Determined users with special software can strip them — treat permissions as a strong lock, not a vault.
I forgot the password. Can you recover it?
No — and that's the point of encryption. We never see your password; it exists only in your head and your browser session. Keep a copy somewhere safe.
Does protection change my document's content?
No. Pages, text, and images are untouched; only the file's security envelope changes.
Is my password sent to a server?
Never. Both the file and the password stay in your browser; only the encrypted result is written for download.
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继续——处理 PDF 所需的其他工具，全部免费、全部本地运行。