Password Protect PDF
Encrypt a PDF so it asks for a password before it opens.
Runs in your browser. Your file and password are never uploaded.
Protected PDF ready
Opening it will ask for the password you chose. Send the password separately from the file — by text or a call rather than in the same email.
How PDF password protection works
Protecting a PDF encrypts it. Every page's text, images and fonts are scrambled with AES-256 using a key derived from your password, and only someone who types that password can rebuild the key and read the file. It is not a gate in front of readable content: without the password, the document is noise. That is why a forgotten password cannot be reset — there is nothing to reset, only a key that no longer exists anywhere.
Open password and restrictions
The password you type is the open password (Adobe calls it the Document Open password). The optional restrictions are something else: flags asking the viewer to disable printing, copying text or editing. Acrobat, Preview and browsers honour them, but they are an instruction rather than encryption, and anyone who can open the file can find software that ignores them. Rely on the open password for confidentiality and treat restrictions as a polite request.
Choosing a password
AES-256 is not the weak point; the password is. Software can try millions of guesses a second against a stolen file, so a short word or a date falls quickly, while three or four unrelated words or a dozen random characters do not. If you need to generate one, the password generator does it in your browser too. Send the password by a different route from the file.
Removing it again
To take the password off a PDF you can open, use Unlock PDF. Protecting a file that is already locked asks for its current password first, and the new password replaces the old one.
Frequently asked questions
How do I password protect a PDF for free?
Choose the PDF, type a password twice, and click Protect PDF. The download asks for that password every time it is opened — in Acrobat, Chrome, Edge, Preview, or a phone. It takes seconds and there is no account, watermark or limit.
Is my PDF or password uploaded?
No. The file is encrypted inside your browser tab, and neither the document nor the password leaves your device. That is the point of protecting a file in the first place.
How strong is the encryption?
AES-256, the strongest method the PDF standard defines and the one ISO 32000-2 recommends. With a long, unpredictable password the file cannot practically be opened without it. A short or guessable password is the weak point, not the encryption, so use eight characters or more for anything sensitive.
What if I forget the password?
It cannot be recovered or reset — not by us, since the password never reaches us, and not by anyone else. Keep a copy of the unprotected original, or store the password in a password manager, before you send the protected file.
Can I stop people printing or copying the PDF?
Yes. Untick Allow printing, Allow copying or Allow editing under Restrictions. Be aware that restrictions are a request to the viewer, not a lock: mainstream apps respect them, but anyone who can open the file can find software that ignores them. The open password is what actually keeps people out.
Will the protected PDF open on any device?
Every current PDF viewer supports AES-256, including Adobe Acrobat and Reader, Chrome, Edge, Firefox, Safari and Preview, and the built-in viewers on iPhone and Android. Only software older than Acrobat 9, from around 2008, cannot open it.