How to add a password to a PDF
- Add one or more PDFs. Drop them on the box or press Select PDF files.
- Type a password. Press Show to check what you typed. The bar under the box gives a rough idea of how hard the password is to guess.
- Add limits if you want them. Tick Also limit printing, copying and changes, choose what stays allowed, and set a second password for the limits (see below).
- Press Protect PDF and download the protected file. With several files, every file gets the same password and you download them together as a .zip.
Before the download appears, the tool opens the new file to check that it needs the password and that every page is there.
How strong the protection is
The file is encrypted with AES-256, the strongest method in the PDF standard. Without the password, the pages can't be read; the file is not just hidden behind a prompt. Adobe Acrobat and Reader, the PDF viewers built into Chrome, Edge, Firefox and Safari, macOS Preview and most current apps can open it. Some very old PDF readers can't, because they don't know AES-256.
The protection is only as good as the password. Short words and number patterns can be guessed by software that tries millions of passwords. A password of three or four unrelated words, or 12 or more mixed characters, is a good choice.
There is no way to recover a lost password. Not even this tool can open the file without it, so keep the password somewhere safe, such as a password manager.
Open password and permissions password
The open password is needed to see the file at all. The optional permissions password controls the limits: whether people who open the file may print it, copy its text and images, or change it (edit, add comments, fill in forms). It must be different from the open password; otherwise everyone who can open the file could also remove the limits.
Be aware that the limits are a request, not a lock. Mainstream PDF readers follow them, but some apps ignore them. Only the open password truly keeps people out.
Private and fast
The file and the password stay on your device. Encryption runs in your browser, so nothing is uploaded and the password is never sent anywhere. Protecting a 20 MB file takes about a second or two.
Frequently asked questions
Can I remove the password later?
Yes. Use Unlock PDF with the password, or open the file in a PDF reader that can save a copy without a password.
Does a password change the file's content?
No. The pages, text, images, links and bookmarks stay the same. Only the way the file is stored changes.
Can I protect a PDF that already has a password?
Remove the old password first with Unlock PDF, then add the new one here.
Is a digital signature still valid after protecting?
No. Adding a password changes the file, so add the password first and sign afterwards if you need both.
This tool works in your browser: your files are processed on your device and are never uploaded. Check the result before you share it or delete the original.