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Password protect a PDF - AES-256 encryption in your browser

Encrypt a PDF with an open password before you email it or upload it to the cloud. AES-256 encryption runs in your browser, and neither the file nor the password goes to a server.

  • Free
  • No sign-up
  • Private
  • Runs locally

A lost password cannot be recovered

The file is encrypted in your browser, and the password is never sent or stored anywhere. We cannot remind you of it or reset it, and without it nobody can open the file. Keep the password somewhere safe before you send the document on, and keep a copy of the original.

Drag & drop files here

or click to choose from your device

PDF file · processed locally in your browser

Your file is never uploaded. Everything happens in your browser.

How to password protect a PDF

  1. 1.

    Open the PDF

    Drop the document onto the area above or choose it from your device. If the file already has a password, enter it and the new one will replace the old one.

  2. 2.

    Set the open password

    Type the password twice or click "Generate a strong password". A bar shows a rough password strength. Save the password before you go on.

  3. 3.

    Choose locks (optional)

    You can block printing, copying and editing. Keep in mind that these are flags in the file, not a hard security measure.

  4. 4.

    Protect and download

    The tool encrypts the file and checks the result: the file must not open without the password, and with it the page count must match. Then you download the protected PDF.

Open password versus permission locks

These are two different protections, and only one of them protects the content.

Open passwordPrint, copy and edit locks
What it doesEncrypts the content, so the file will not open without the passwordStores flags in the file saying what a program should not do
What enforces itThe AES-256 encryption itselfThe goodwill of the program that opens the file
Can it be removedNot without the password (short of guessing it)Yes, anyone can strip them from the file, including with Unlock PDF on this site

Most PDF programs respect the locks, but there is no guarantee that every one does, and a screenshot is always possible. If the confidentiality of a document matters, rely on the open password and treat the locks as an extra that discourages accidental copying or changes.

Choosing a password

AES-256 is strong, so the password becomes the weakest link. A short or common password can be guessed no matter how strong the encryption is.

  • Use a long password of random characters, such as the 20-character one from the "Generate a strong password" button, or several randomly chosen words.
  • Avoid names, birthdays and passwords reused from other accounts.
  • Send the password by a different route than the file, for example by text message or phone, not in the same email.
  • Keep the password in a password manager. A lost password cannot be recovered, and without it the file cannot be opened.

A password can be up to 127 bytes, and accented letters take 2 bytes each. It cannot start with @ or "--". Some older programs do not recognize characters outside the basic set, so the tool warns you when you use them.

What to do with the file before protecting it

A file with a password will not open in other PDF tools until you supply the password, so make every change first: merge files, sign the document, add a watermark or reduce the size.

The protected file is a new version of the document: the pages, text and images are the same, but digital signatures in the original may stop being valid. Keep the original in case you lose the password.

Will the recipient be able to open it

Modern PDF programs, including browsers and viewers on computers and phones, support AES-256 encryption. Older or simplified programs may not. For an important delivery, ask the recipient to try opening the file.

Frequently asked questions

Is AES-256 encryption in a PDF secure?

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AES-256 is a strong algorithm, and the password decides how secure the file really is. A short or common password can be guessed regardless of the algorithm, so use a long, preferably random one.

What if I forget the password of a protected PDF?

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The file cannot be opened. The password is not stored anywhere, so we have no way to remind you of it or reset it. Keep the original and keep the password in a password manager.

Does blocking printing and copying really protect the file?

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Only partly. These are flags in the file that most programs respect, but nothing technically enforces them. They can be removed from the file without a password. Only the open password protects the content.

Are my file and password sent to a server?

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No. The file is encrypted in your browser, and the password is never sent or stored anywhere. The encryption module (about 1.3 MB) loads from the same server as the page, not from an external service.

Can I protect a PDF that already has a password?

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Yes. Enter the current password after opening the file. The new password and AES-256 encryption replace the old protection.

Can the password contain accented letters?

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Yes, but some older programs may not recognize them, so the tool shows a warning. A password can be up to 127 bytes, and accented letters count as 2 bytes each.

Do screen readers still work on a file with locks?

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Yes. Blocking copying does not stop screen readers from reading the content, so the document stays accessible to blind users.

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