Add Password to PDF Free Online

How to password-protect a PDF online

1. Drop your PDF onto the upload zone or click Choose File to select it from your device.
2. Type your desired open password in the User Password field and confirm it in the second field. Optionally set an Owner Password to control printing and copying permissions separately.
3. Click Add Password. Encryption runs locally in your browser — no file is uploaded.
4. Download the protected PDF. The file is locked with AES-256 and ready to share.

AES-256 encryption and PDF password types

PDF files support two distinct password layers. The user password (open password) gates access to the document entirely — anyone who receives the file must enter it before the PDF will open. The owner password (permissions password) does not prevent opening the file but restricts what a reader can do with it: printing, selecting and copying text, filling forms, or making edits can each be locked independently. VoxScan applies AES-256 in CBC mode, the strongest encryption level in the PDF 1.7 and PDF 2.0 specifications. A well-chosen password under AES-256 offers no practical path to brute-force recovery, which is why forgetting it means permanent loss of access. Use a password manager and store the credential before encrypting.

When to use PDF password protection

Password-protecting a PDF is appropriate any time the document contains information that should only reach its intended recipient. Common cases include emailing tax returns or financial statements where the password is shared via a separate channel, distributing signed contracts before countersigning, sending medical records or insurance documents, protecting intellectual property in a draft report, or sharing confidential HR documents with a specific individual. If you need to restrict what a recipient can do with a file they are already authorized to open — prevent printing or copying — set an owner password alongside or instead of a user password.

Frequently asked questions

What encryption does this tool use?

The tool applies AES-256 encryption, the same cipher used by government agencies and financial institutions. AES-256 is the strongest standard defined in the PDF specification and is supported by all modern PDF readers.

What is the difference between a user password and an owner password?

A user password (also called an open password) is required to open and read the file. An owner password controls permissions — it restricts what someone who has opened the document can do, such as printing, copying text, or editing. You can set one or both. If you set only an owner password, the file opens freely but actions like printing remain locked until the owner password is entered.

Can I recover my password if I forget it?

No. Password recovery is not possible from this tool, and that is by design. AES-256 encryption with a strong password cannot be brute-forced in any practical timeframe. Store your password in a password manager before encrypting. If you lose the password, the file is inaccessible.

Is it safe to type my password here? Does it get sent anywhere?

Yes, it is safe. VoxScan runs entirely in your browser using WebAssembly. Neither your file nor your password is ever transmitted to a server. Encryption happens locally on your device, and nothing leaves your machine.

Can the password be removed later?

Yes. Use the Remove Password tool on VoxScan to decrypt a protected PDF. You will need to supply the correct open password to do so. The process is also local — no file is uploaded.