All Converter Pro
在线 保护 PDF
在线免费为 PDF 添加密码保护。AES 加密意味着没有密码就无法打开文件。保护合同、工资单和记录。
关于此 保护 PDF 工具
Protect PDF encrypts a document with a password so it cannot be opened by anyone who does not have it. This is real AES encryption applied to the file itself, not a soft lock: the protection travels with the file, working the same in Adobe Reader, browsers, phones and email attachments. Use it before sending payslips, contracts, medical records, financial statements or any document with personal data over email or messaging apps - email itself is not encrypted, so a password on the attachment is the practical safeguard. Choose a strong password and share it through a different channel than the file (for example, send the PDF by email and the password by phone or text message).
如何使用 保护 PDF
- 打开工具并添加您的文件、文字或数值。
- 检查可用选项,例如页面范围、输出格式、质量、密码或语言。
- 开始处理,并在完成前保持浏览器窗口打开。
- 下载结果,如有需要可继续使用相关工具。
实用提示
- 对于扫描的 PDF,支持 OCR 的工具会尽可能自动运行文字识别。
- 对于大文件,在通过邮件分享或上传到门户网站之前,请使用压缩工具。
- 为获得最佳效果,请上传扩展名正确的干净文件,避免使用损坏的文档。
When to password-protect a PDF
Sending payslips, tax documents or bank statements by email - attachments are frequently forwarded and mailboxes get breached.
Sharing contracts and agreements that contain personal data, pricing or terms not meant for third parties.
Storing scans of passports, IDs and certificates in cloud folders that other people or apps can access.
常见问题
How strong is the protection?
The file is encrypted with the AES standard used by PDF readers. Without the password the content cannot be read; there is no backdoor or recovery, so store the password safely.
如果我忘记密码会怎样?
The document cannot be recovered without it - that is the point of encryption. Keep a copy of the password in a password manager, or keep an unprotected copy in a safe location.
Will the password work in all PDF readers?
Yes. Password protection is part of the PDF standard, so Adobe Reader, browser viewers, macOS Preview and mobile apps all prompt for the password before opening the file.
Can I remove the password later?
Yes. Use the Unlock PDF tool with the correct password to produce an unprotected copy.
Should I email the password together with the file?
No. Sending both through the same channel defeats the purpose. Share the password through a second channel, such as a text message or phone call.
保护 PDF 免费吗?
Yes. Encryption is free, with no signup and no watermark.