Password-protect a PDF
Lock a document with a password
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Drop your file here
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PDF document · Up to 100 MB
How do you put a password on a PDF?
The tool encrypts the document with AES-256 and hands it back openable only with the password you chose. Printing and screen-reader access are deliberately left on — a password restricts who can open the document, it does not make it unreadable.
What a password does not do
- It offers no way to recover the password: a forgotten one cannot be opened by anyone, including us.
- It does not certify the document with a digital signature.
- It keeps no copy anywhere — you have to save the protected file yourself.
Example: a draft going to a supervisor
A 40-page draft was given a password. The resulting file asked for it in Adobe Acrobat, in the browser and in phone readers alike; once entered, the document opened in full and printing worked. The file grew by roughly one per cent — encryption adds bookkeeping, but changes nothing in the content.
When sending unpublished results
Unpublished experimental results, a description being prepared for a patent, or a dissertation chapter that has to stay closed until the defence are all commonly sent by email. If the mailbox is compromised, or the message goes to the wrong address, the attachment is simply open. A password is not the only protection here, but it is the cheapest: tell the recipient over another channel, a phone call for instance. Writing the password into the same message cancels the protection entirely. When you choose a password, decide in advance where you will keep it: there is no recovery, and a forgotten password closes the document for good. One more thing: the protection applies to this copy alone — if the file was already sent without one, those copies stay open.
| Accepts | PDF document |
|---|---|
| Returns | PDF document |
| Maximum file size | up to 100 MB |
| Maximum pages | up to 500 pages |
| Several files at once | No |
| Is the file uploaded | No — everything runs in your browser |
| Price | Free |
| Account needed? | To download — yes (free) |
Frequently asked questions
What happens if I forget the password?
The document will not open. AES-256 cannot be opened without the password, and neither this tool nor we can help with that. Keep the password somewhere separate.
Which encryption is used?
AES-256, the only algorithm ISO 32000-2 still recommends. The older RC4 variants are considered broken and are not used here.
Is printing restricted?
No. Printing and screen-reader access are deliberately left open: blocking them protects nothing and only makes the document harder to use.
Is the password sent to a server?
No. Neither the password nor the document leaves your browser — the encryption happens here, on your device.