How to use
- Drop a PDF onto the box or click to choose it. If it is already locked, enter its current password first.
- Type an open password and confirm it. Use the strength hint under the field to pick something long enough.
- To block printing, copying or editing, untick those actions and set a permissions (owner) password.
- Press Protect PDF and download the locked file.
Open password vs. permissions password
| What it does | If left empty | |
|---|---|---|
| Open password | Asked for when the file is opened; without it the content can’t be read | Anyone can open the file (restrictions-only mode) |
| Permissions password | Lifts or changes the print, copy and edit restrictions | A random password if restrictions are set, otherwise the same as the open password |
| Permission | Unticking it blocks |
|---|---|
| Printing | All printing, including high-quality printing |
| Copying | Copying or extracting text and images (extraction for screen readers stays allowed) |
| Editing | Changing content, adding comments, filling forms, inserting, deleting or rotating pages |
Encryption and password strength
Files are encrypted with AES-256, the method recommended by the PDF 2.0 standard (ISO 32000-2). They open in Acrobat Reader X and later and in the built-in PDF viewers of current browsers such as Chrome and Edge; very old software like Acrobat 9 and earlier may not open them.
Strong encryption doesn’t help if the password is short, so the tool estimates strength from length and character variety:
| Example | Estimate | Rating |
|---|---|---|
1234 |
A simple sequence | Weak |
Tr0ub4dor |
9 mixed-case letters and digits, about 54 bits | Fair |
correct horse battery staple |
A four-word passphrase, about 165 bits | Strong |
Aim for 12 or more characters, or a passphrase of four or more unrelated words. The password generator can make one for you. The meter is an estimate, not a guarantee of how hard a password is to guess.
Things to know
- The file and passwords stay in your browser and are never uploaded or stored; the fields are cleared once the PDF is protected.
- If the open password is lost, nobody — this tool included — can realistically open the file. Keep the original somewhere safe or write the password down.
- Restrictions only work when the viewer honors them. Acrobat and most viewers do, but some programs ignore them, so add an open password if the content must stay private.
- Re-saving a digitally signed PDF can make its signature show as modified.
- To remove the password later, use Unlock PDF.
FAQ
How should I share the password?
Not in the same email as the PDF — anyone who sees that email could open the file. Send it separately, by text message or a chat app.
Can I block copying without an open password?
Yes. Leave the open password empty, untick “Copying” and set a permissions password. Anyone can open the file, but viewers that honor restrictions won’t let them copy from it.