Protect PDF
Encrypt a document so it asks for a password before it opens. The encryption happens on your device, so neither the file nor the password goes anywhere.
Runs entirely in your browser. Your files are never uploaded.
How to use Protect PDF
- 1Pick a PDF, or drag it onto the box above.
- 2Choose a password and type it twice.
- 3Decide what the person opening it may do.
- 4Press Protect PDF and download the encrypted file.
What the password actually does
The document is encrypted with AES-256, which is the strong option the PDF specification defines. Without the password the contents cannot be read at all. That part is real cryptography, and it holds.
We can state that with some confidence because the test suite checks it the hard way: after encrypting, it tries to open the file with the ordinary PDF library the rest of this site runs on, which has no decryption support whatsoever. If that library can still read the file, the test fails.
The permission checkboxes are weaker than they look
Printing, copying, modifying and annotating are flags stored inside the document. A reader that respects them will grey out the relevant menu items. A reader that does not will ignore them completely, and plenty do.
So treat permissions as a statement of what you intend rather than a restriction you can rely on. Anyone who can open the document can get the contents out of it one way or another. The password is the part that matters.
Nobody can recover this password
There is no reset, no recovery and no back door. Lose the password and the document is gone, which is the entire point of encrypting it. Put it in a password manager before you close the tab.
This matters more than people expect, because the file you have just encrypted usually replaces the one you had. Keep the unencrypted original somewhere until you are certain the password works.
Owner passwords
A PDF can carry two passwords: one to open the document and one that bypasses the permission limits. This tool sets both to what you type, which is what people mean by putting a password on a file. Documents needing different passwords for opening and for editing are a specialist case we have not built for.
Limits
- 100 MB per file.
- A document that already has a password must be unlocked first.
- Permission flags depend on the reader honouring them.
- One password, used as both the open and owner password.
- PDF/A documents cannot be encrypted at all: the standard forbids it.
Frequently asked questions
- How strong is the encryption?
- AES-256, the strongest the PDF format defines. The strength of your particular file comes down to the password you chose, which is the usual weak point.
- Can you recover my password if I forget it?
- No. Nothing about the password is stored or sent anywhere, there is no record of it, and the encryption is genuine. A forgotten password means a lost document.
- Does the password get uploaded?
- No. The encryption runs in your browser, so the password is used on your device and never leaves it.
- Why can a reader still print it when I turned printing off?
- Because permission flags are advisory. Readers that respect them will stop you; readers that do not will ignore them. The format offers no way to enforce it.