Protect PDF
Encrypt with a password to control access.
How to use Protect PDF
- 01
Upload your PDF
Add the document you want to protect — a financial report, a contract, personal records, or any sensitive file.
- 02
Set a password
Choose a strong password. The tool encrypts the entire PDF with 256-bit AES so only someone with the password can open it.
- 03
Download the protected PDF
Save the encrypted PDF. Anyone who tries to open it will be prompted for the password first.
Tested and last verified on
About Protect PDF
Add a password to a PDF with real 256-bit AES encryption, so only people with the password can open it. Encryption runs entirely in your browser — the password never leaves your device.
Real encryption, not just a viewing restriction
There are two kinds of PDF password protection, and the difference matters. The first kind — owner passwords that restrict printing, copying, and editing — is essentially a polite request to the viewer software. Many PDF tools ignore these restrictions entirely. The second kind — a user password that encrypts the file's content — is real security. Without the password, the data is unreadable, and no tool can bypass it because the content is mathematically scrambled.
This tool applies the second kind: genuine 256-bit AES encryption. The entire content of the PDF — text, images, metadata — is encrypted so that only the correct password can decrypt and display it. This is the same encryption standard used by financial institutions and government agencies.
How the encryption works
When you set a password, the tool uses it to derive an encryption key through a key-derivation function. That key is then used to encrypt every content stream in the PDF with the AES-256 algorithm. The result is a file that looks like random data to anyone (or any software) that does not have the password. When a viewer opens the file, it prompts for the password, derives the same key, decrypts the content, and displays the document.
The password itself is not stored in the PDF — only a hash is included so the viewer can verify that the entered password is correct. This means there is no way to recover a forgotten password from the file. If you lose the password, the document is inaccessible.
When to encrypt and practical advice
Encrypt documents before emailing sensitive files — financial statements, medical records, legal agreements, identity documents — especially over unsecured channels. Encrypt files before uploading them to cloud storage if you do not fully trust the provider's security. Encrypt archived documents that contain personal data to meet data-protection requirements.
Choose a password that is hard to guess: at least 12 characters with a mix of upper and lowercase letters, numbers, and special characters. Share the password through a separate channel from the document itself — if you email the PDF, send the password by text message or a secure messaging app. And always keep an unencrypted backup in a secure location, because there is no password-recovery mechanism — a forgotten password means the document is permanently locked.
Questions
Everything runs in your browser. How we keep files private
What type of encryption is used?
The tool uses 256-bit AES encryption — the same standard used by banks and government agencies. It is the strongest encryption available in the PDF specification.
Can I open the protected PDF in any viewer?
Yes. Standard PDF encryption is supported by all major viewers: Adobe Reader, Preview, Chrome's built-in viewer, Foxit, and every other compliant PDF reader. The viewer prompts for the password before displaying the content.
Can someone crack the password?
256-bit AES encryption is not practically crackable with current technology. However, a weak password (like '1234' or 'password') can be guessed quickly. Use a strong, unique password with a mix of letters, numbers, and symbols.
Is the password sent to a server?
No. The encryption runs entirely in your browser. The password never leaves your device — it exists only in your browser's memory during the operation.
Part of: Sharing ID documents without leaking them
Mask, redact and strip your Aadhaar, PAN and other IDs before you send them.
- Find and black out Aadhaar and PAN numbers automaticallyChecksum-verified detection, every match shown for review, then true removal — or UIDAI-style masking that leaves the last four digits.
- Permanently remove anything sensitive by handDraw over names, addresses or figures and have the underlying content genuinely deleted, not covered.
- Strip hidden metadata before you share a fileDocuments carry author names, software details and edit history you never intended to send.