Protect PDF
Password-protect any PDF with AES-256 encryption — set a password, download a locked copy. Runs entirely in your browser.
About this tool
Add password protection to any PDF using AES-256-GCM encryption. The password you set is used to derive an encryption key via PBKDF2 with 100,000 iterations — the same standard used by password managers. The entire operation runs in your browser using the Web Crypto API: your PDF bytes and password never leave your device. The encrypted file can be unlocked later using Toolisk's Unlock PDF tool. Free, no sign-up, no watermark.
How to use it
Quick steps to get the most out of this utility.
- 1
Drop your PDF
Any size up to 100 MB.
- 2
Set a password
Min 4 characters. Choose something memorable.
- 3
Confirm & encrypt
One click, AES-256 encryption applied.
- 4
Download the protected copy
Keep your password safe — it cannot be recovered.
When you need to password-protect a PDF
There are many situations where you need to lock a PDF before sharing it: sending a tax return to your accountant, emailing a contract to a client, storing a bank statement in cloud storage, or sharing a confidential report with your team. Password protection ensures that only someone with the correct password can view the file — even if it falls into the wrong hands.
As a concrete example: a 20-page business report at 3.2 MB. After setting a password and clicking Protect, the tool encrypts the file using AES-256-GCM. The resulting file is approximately 3.2 MB (encryption adds negligible overhead — about 37 bytes for the header). The encryption takes well under a second in a modern browser, with the PBKDF2 key derivation being the only noticeable computation.
Why no upload matters for protecting sensitive PDFs
When you protect a PDF using a server-side tool, you are giving that server both your unprotected file and the password you want to protect it with. This means the provider can read your document and knows your password. If the server is compromised, your sensitive data and password are exposed.
Toolisk's Protect PDF tool eliminates this risk. The encryption happens entirely in your browser using the Web Crypto API. Your file is read into memory, the encryption key is derived from your password using PBKDF2, and AES-256-GCM encrypts the PDF bytes. The encrypted result is streamed directly to your download. Nothing is transmitted to any server. This is not a privacy promise — it is how the technology works.
Protect PDF vs Unlock PDF
| Tool | What it does |
|---|---|
| Protect PDF | Encrypts a PDF with a password. The output can only be opened after entering the password in the Unlock PDF tool. |
| Unlock PDF | Removes password protection from both standard PDF passwords and Toolisk-encrypted PDFs. Enter the password and download the unlocked copy. |
| Compress PDF | Reduce file size before encrypting — useful for large PDFs being shared via email. |
| Merge PDF | Combine multiple PDFs before protecting them as a single encrypted file. |
Frequently asked questions
Is this safe? Does it upload my PDF?+
No upload whatsoever. Encryption runs entirely in your browser using AES-256-GCM via the Web Crypto API. Your PDF and password never leave your device, are never sent to a server, and are never logged.
What is the maximum file size?+
PDFs up to 100 MB are accepted. Files over 30 MB may be slower to encrypt, especially on mobile. The encryption uses PBKDF2 with 100,000 iterations for key derivation, which adds a brief delay.
Does it work offline?+
After the page has loaded once, yes — all encryption runs locally in your browser using the Web Crypto API which works offline.
Will this work on iPhone / iPad?+
Yes, on modern iOS Safari which supports the Web Crypto API. iOS limits per-tab memory, so very large PDFs (>50 MB) may encounter memory constraints.
How secure is the encryption?+
It uses AES-256-GCM — the same algorithm used by TLS and modern disk encryption. The key is derived using PBKDF2 with SHA-256 and 100,000 iterations, making brute-force attacks impractical.
Can I open this PDF in any PDF reader?+
Toolisk-protected PDFs use a custom AES-256 encryption format. They can only be unlocked using Toolisk's Unlock PDF tool. This approach ensures true client-side encryption without needing server-side PDF processing.
What happens if I forget my password?+
There is no way to recover it. The encryption is mathematically irreversible without the correct password. Keep it in a safe place.
Is this the same as standard PDF password protection?+
No. Standard PDF password encryption requires server-side libraries or heavy WASM modules. Toolisk's approach uses the browser's built-in Web Crypto API for AES-256 encryption, keeping everything local and lightweight.
Keep exploring
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