Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Add a password to a PDF with AES-256 encryption, and optionally restrict printing, copying and editing -- the file never leaves your browser.
Choose a PDF to password-protect.
This tool adds a password to a PDF, so it can only be opened by someone who knows it. The file is encrypted with AES-256, the strongest encryption the PDF standard defines, and everything is encrypted -- page content, images, links, form data, and document properties such as the title and author. You can also restrict printing, copying and editing. The whole process runs in your browser; the PDF and the password never leave your device.
Choose or drop a PDF. Type the password that will be needed to open it, and type it again to confirm. If you also want to limit what people can do with the opened file, tick "Also restrict printing, copying or editing", set a separate permissions password, and choose what to allow. Click Protect PDF and download the protected copy, which is saved with "-protected" added to the file name. Keep the original until you've checked that the protected copy opens with your password.
The PDF standard has two passwords. The open password (user password) is needed to view the file at all; without it, the content is unreadable ciphertext. The optional permissions password (owner password) controls restrictions on printing, copying and editing. With AES-256, the key is derived from the password through repeated SHA-2 hashing, which deliberately slows down every guess an attacker makes.
A protected PDF can be copied, so anyone who gets hold of it can try passwords offline, as fast as their hardware allows, with no lockout. AES-256 itself can't be broken, but a short or predictable password can simply be guessed. The tool asks for at least 8 characters and warns if the passwords don't match, but longer is much better: a random password of 12 characters or more, or a passphrase of five or six random words, is out of reach of guessing. The Password Generator can create either, and the Password Strength Checker shows how a password you have in mind would hold up.
Restrictions on printing, copying and editing are recorded in the file, and mainstream readers such as Adobe Acrobat honour them. But they are a request, not a lock: anyone who can open the file can, with the right software, ignore them. Use restrictions to signal how a document should be used -- for example, to discourage casual copying from a report -- and rely on the open password for real confidentiality. The permissions password must differ from the open password; if they were the same, everyone who could open the file could also lift the restrictions.
Say you're emailing a payslip to an accountant. Drop the PDF in, type a long password such as a five-word passphrase, confirm it, and click Protect PDF. Send the protected file by email and the password by a different route -- a text message or a phone call -- so that someone who intercepts the email doesn't also get the password. If the accountant shouldn't edit the figures, tick the restriction option, set a separate permissions password that only you know, and leave "Editing the content" unticked.
To remove a password later, use Unlock PDF. To combine several files before protecting them, use Merge PDF.
No. Encryption happens in your browser. Neither the file nor the password is sent to a server or stored, so there is nothing on our side that could be leaked.
It can't be recovered. There is no back door in AES-256 and the tool keeps no copy of your password, so a forgotten password means the protected copy is lost. Store the password in a password manager before you delete the original file.
The encryption itself is considered unbreakable with current technology. The weak point is always the password: protection is as strong as the password is hard to guess, which is why a long random password or passphrase matters.
Yes -- that's the default. Without the restriction option, anyone who knows the password can open, print, copy and edit the file normally.
Yes. Document properties are encrypted along with the content, so even the title isn't readable without the password.