Protect PDF with Password
Password protect a PDF with AES-256 encryption in your browser. Set a password to open, plus optional printing, copying and editing permissions.
Tip: this password is short. A longer one (12 characters or more, or a few random words) is much harder to guess.
How to password protect a PDF
- Drop a PDF file on the drop zone, or click it to choose one. The tool shows its name and size.
- Type the Password to open the PDF, then type it again in Confirm the password. Tick Show passwords to check what you typed.
- Optionally, set the Permissions: Printing (Allowed, Low resolution only or Not allowed), Changes (Allowed, Comments and form filling only, Form filling only or Not allowed) and Allow copying text and images.
- Optionally, enter a Permissions password (optional). It must be different from the password to open.
- Click Protect PDF. The first time, the encryption engine (qpdf compiled to WebAssembly) is loaded; then the file is encrypted in a moment.
- Click Download the protected PDF. The file is saved with
_protectedadded to its name.
What the protection really does
The password to open is real encryption. The tool uses AES-256, the strongest method defined by the PDF standard (PDF 2.0, security handler revision 6). Every page, image and font is encrypted, and nobody can read the content without the password. Any modern reader (Adobe Acrobat, Preview, browser viewers, Foxit, Okular…) asks for it when the file is opened.
The permissions are different: they are only flags stored in the file. A reader that respects them greys out printing, copying or editing, but the content itself is readable by anyone who has the password to open. Some programs simply ignore these flags. Use them to signal your intentions and to prevent accidental edits, not to protect secrets.
The permissions password (also called the owner password) is what lets someone change or remove those restrictions later. If you leave it empty, the tool generates a random 24-character one that is never shown: nobody will then be able to change the permissions without removing the protection completely.
Choosing a good password
- Length matters most. A short password can be guessed by trying millions of combinations offline; the tool shows a tip when yours has fewer than 8 characters. Aim for 12 characters or more, or a few random words.
- Passwords are limited to 127 bytes (about 127 letters, fewer with accented characters), as the PDF standard requires.
- Send the password through a different channel than the file, for example by text message when the PDF goes by email.
- Keep it somewhere safe. AES-256 has no back door: if you forget the password, nobody can recover the content, including this tool.
Good to know
- A PDF that is already encrypted is refused. Remove its password first (you need to know it), then protect it again with new settings.
- Encryption does not change the content, the layout, the bookmarks or the form fields of the document.
- Everything happens in your browser: the file and the passwords are never sent to a server.
Frequently asked questions
Is AES-256 PDF encryption secure?
Yes. With a long, unpredictable password, AES-256 cannot be broken in practice. The weak point is the password itself: short or common passwords can be guessed.
Can people print or copy my PDF despite the permissions?
Possibly. Permissions are advisory flags that depend on the reader honouring them. Most well-known readers respect them, but some tools ignore them. Only the password to open truly keeps the content private.
What if I forget the password?
It cannot be recovered. Keep an unprotected copy of the original somewhere safe, or store the password in a password manager.
Why must the permissions password be different?
If both passwords were the same, anyone able to open the file could also lift the restrictions, which would make the permissions pointless.
Will the protected PDF open everywhere?
AES-256 is supported by every reader released in the last decade. Very old software (before Acrobat 9, around 2008) may not open it.
Related tools
- Unlock PDF Remove the password from your own PDF in your browser. Enter the password you know and download an unlocked copy. No cracking, no upload.
- Edit PDF Metadata View and edit PDF metadata in your browser: title, author, subject, keywords, creator, producer and dates, or remove it all. No upload.
- Flatten PDF Flatten a PDF in your browser. Turn form fields, comments, highlights and drawings into ordinary page content that can't be edited. No upload.
- Password Generator Free password generator that creates strong random passwords of 4 to 128 characters in your browser with a secure RNG. Nothing is stored or sent.