Encrypt a PDF Online
Most tools that promise to encrypt a PDF online do it by uploading your file to their server, encrypting it there, and sending it back, which means your unencrypted document and the password you chose both sit on someone else's machine during the process. That defeats much of the point of encrypting a private file. FixTools works the opposite way. The encryption runs in your browser using @cantoo/pdf-lib, so the file is locked on your own device and never uploaded at all. You add the PDF, type and confirm a password, and download an AES-encrypted copy that requires the password to open in any reader. It is online in the sense that you reach it through a web page, but the sensitive work happens locally, so you get browser convenience without handing your document and password to a third party. The password cannot be recovered afterwards, so store it safely.
- Cost
- Free tier
- Sign-up
- Not required
- Processing
- Tool-specific
- Privacy
- Clearly disclosed
AES encryption applied in your browser, not on a server
The file is never uploaded during encryption
Your password is never transmitted or stored
PDF Tool
Password Protect PDF
Open the tool to see its processing method, supported formats, and current limits.
🚀Open Password Protect PDFFree tier · No account · Limits shown before processing
The difference between online and local encryption
When a site encrypts your PDF on its server, your original file has to travel there in the clear, and the password you type usually goes with it so the server can apply it. Even if the company deletes everything afterwards, there is a window where your private document and its key exist on hardware you do not control. For genuinely sensitive files, that window is the whole risk.
FixTools removes it by doing the encryption in the browser. The @cantoo/pdf-lib library applies an AES open password to the file on your device, and only the finished, encrypted PDF is ever produced. Nothing is sent out, so there is no server copy to trust, delete, or worry about. Turning on airplane mode after the page loads and encrypting anyway is the simplest way to prove the file is staying put.
How to use this tool
Add your PDF, type and confirm a password, and click Protect PDF. The file is encrypted with AES locally and downloads as a protected copy that never touched a server.
How It Works
Step-by-step guide to encrypt a pdf online:
- 1
Open the tool
Launch FixTools Password Protect PDF in your browser. There is no account to create.
- 2
Add your PDF
Upload the file you want to encrypt from your device.
- 3
Type and confirm a password
Enter the password, then repeat it in the confirm field so the tool verifies they match.
- 4
Encrypt the PDF
Click Protect PDF. AES encryption is applied to the file locally in your browser.
- 5
Download the encrypted file
Save the protected copy. It now requires the password to open in any reader.
Real-world examples
Common situations where this approach makes a real difference:
Genuinely sensitive file
Someone encrypting a document with financial or health details wants it locked without ever uploading it.
Privacy-conscious user
A user who distrusts upload-based tools encrypts the file locally and verifies nothing leaves the browser.
Regulated data
A small firm handling client records avoids sending files through a third-party server to lock them.
Public or shared network
A traveler encrypts a document on hotel wifi without transmitting it over the network at all.
Pro tips
Get better results with these expert suggestions:
Prove it stays local
Load the page, switch on airplane mode, then encrypt. It still works, which shows the file never leaves the device.
Use a long passphrase
AES is only as strong as the password. A long passphrase resists guessing far better than a short word.
Save the password securely
Store it in a password manager, because a forgotten password on an encrypted file cannot be recovered.
Keep a backup of the original
Hold on to the unencrypted file somewhere safe in case you lose the password.
Frequently asked questions
Related guides
More use-case guides for the same tool:
Related tools
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PDF Compressor
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Watermark PDF
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Ready to get started?
Open Password Protect PDF to review its free limits and processing method.
Open Password Protect PDF →Free tier · No account needed · Transparent limits