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Upload one PDF - or up to 3 with a free account - from your device, or pull them from Google Drive, Dropbox, or OneDrive. Without an account: 1 file, up to 80 MB. With a free account: up to 3 files at once, 80 MB each (120 MB total).
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Type the password you want to use: 4 to 20 characters, any mix of letters, numbers, and symbols. Protecting several files? Set one shared password for all, or a different password for each.
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Re-enter the password to confirm. Type carefully - we have no way to recover a lost password later.
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Click Protect PDF. The file is encrypted with 256-bit AES so only people with the password can open it.
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Download your secured PDF, save it back to the cloud, or send it straight into another tool like Merge or Sign - the protected file is carried across, no re-upload.
AES-256 encryption
Industry-standard 256-bit AES encryption is applied to the entire document - the same standard used by banks and governments.
Password to open
Anyone trying to open the file in any PDF reader will be prompted for your password before they can see the contents.
Set permissions
Beyond the open password, choose whether viewers can print, copy text and images, or edit the file - each restriction is enforced with a separate 256-bit owner key.
Works everywhere
The protected PDF opens normally in Adobe Acrobat, browsers, mobile readers, and any standards-compliant PDF tool.
One password or per-file
When protecting several PDFs, apply one shared password to the whole batch, or set a different password for each file.
Clear password rules
Passwords are 4 to 20 characters using letters, numbers, and standard keyboard symbols (not starting with a dash), with a live strength meter and re-enter-to-confirm before encrypting.
Batch processing
With a free account, protect up to 3 PDFs at once (80 MB each, 120 MB total). Each becomes its own encrypted file, delivered as a ZIP.
Cloud import & save
Pull files from Google Drive, Dropbox, or OneDrive, and save the secured PDF straight back - no local download step.
Workflow Ready
Send the secured PDF straight into Merge, Sign, or any other tool - the file is carried across, so there is no need to re-upload.
Auto-deleted from servers
Files are processed over HTTPS and deleted from our servers shortly after the job finishes. We never store your password.
Free, no watermark
No watermark on the PDF, no signup needed for a single file, no per-day cap on protections.
PDF 怎么设置密码保护？
在上方添加 PDF，输入密码并再次确认，然后加密。下载的副本每次打开都需要输入密码。完全免费，无水印，无需注册。
PDF 加密有多安全？
文件采用 256 位 AES 加密，这是 PDF 标准中最强的加密方式，没有密码无法读取内容。真正的薄弱环节是密码本身：请使用 4 到 20 位字母、数字和符号的组合，避免姓名和生日。
怎么设置禁止复制、禁止打印、禁止编辑？
加密前在权限选项中关闭打印、复制文字和图片或编辑。常见的 PDF 阅读器会阻止这些操作。需要注意的是，这类权限限制只是“君子协定”：知道打开密码的人可以用常见工具去除它们，所以只把密码告诉信任的人。
PDF 设置密码后还可以打印吗？
可以。只要知道密码就能打开并打印，除非你在加密前关闭了打印权限。
能只限制编辑、不设置打开密码吗？
本工具不支持。它总是会设置打开文件所需的密码，打印、复制和编辑的限制是在此基础上附加的。
密码可以用哪些字符？
4 到 20 位：英文字母 A–Z、a–z、数字和常用键盘符号，不能以短横线开头。不支持中文字符作密码，因为很多 PDF 阅读器无法可靠地输入中文密码。
PDF 设置密码忘记了怎么办？
密码无法找回，我们和其他任何人都做不到，这正是加密有效的原因。请把密码保存在安全的地方，或在安全位置保留一份未加密的副本。
可以批量给 PDF 加密吗？
免费账户一次最多 3 个 PDF（单个 80 MB，总计 120 MB），可以共用一个密码，也可以每个文件设置不同密码。加密后的文件打包成一个 ZIP 下载。
手机上怎么给 PDF 加密？
在手机浏览器（Safari、Chrome 等）中打开本页，添加 PDF，设置密码后加密即可，无需安装 App。加密后的 PDF 保存到下载目录。
PDF 加密后如何取消？
使用 解密 PDF，输入一次密码，就能得到一份打开时不再需要密码的副本。
密码安全吗？
安全。密码通过 HTTPS 加密传输，只用于加密你的文件，用完即删除。文件在一小时内自动删除。在 浏览器模式 下，加密在你自己的设备上完成，不上传任何内容。
