Protect PDF

Protect PDF puts a password on a PDF. Nobody can open the file without it: the pages are encrypted with AES-256, the strongest encryption a PDF can carry, which every current PDF reader understands. You can also choose what someone who opens it may do — print it, copy text out of it, change it. Before the file is offered, it is opened again: it must ask for a password, open with yours, carry the permissions you chose and still have every page.

1. Choose a PDF, or drop it on the page. You can merge, reorder, sign or redact first — the password goes on the file you download.
2. Type a password twice. The note under it says how hard it is to guess.
3. Untick what readers may not do once the file is open: printing, copying, changes. For restrictions, you can add an owner password that lifts them.
4. Press Protect and download. The file is encrypted, checked, and offered. Or press Use for every download, and every PDF you download from the workspace gets the password.

• If the password is lost, the file cannot be opened — not by us, not by anyone. Keep it somewhere safe, such as a password manager.
• The protection is only as strong as the password. Short or common passwords can be guessed by software trying millions a second; four or five unrelated words, or twelve mixed characters, are far stronger.
• Restrictions on printing, copying and changes are a request that most readers respect, not a lock: anyone who can open the file can find a program that ignores them. Only the open password keeps people out.
• A protected PDF made here opens in Adobe Acrobat and Reader, browsers, Preview on Mac and phone readers released in the last ten or more years. Very old readers that do not support AES-256 cannot open it.
• Files up to 300 MB. Bookmarks and attachments of the original are not carried over, and a digital signature in the original is no longer valid.
• Your file and your password stay in this browser tab. Encryption is done by qpdf, an open-source PDF program, running in the tab as WebAssembly; neither the file nor the password is uploaded, stored or sent anywhere. The page downloads its own code and qpdf (about 0.44 MB compressed) from toolsdev.in, and no request carries your file. Nothing is kept: closing the tab ends the session.

The password never leaves your device: it is passed to qpdf inside this tab, used to encrypt the file and then discarded with the page. Your browser's network panel shows nothing leaving while it works — only qpdf itself arriving, the first time.

A second password that lifts the restrictions. Someone with the open password can read the file; someone with the owner password can also print, copy and change it. Left empty, a random one is used and not kept.

Add them all, then split them into separate files with the Split tool after setting the password with Use for every download: each part in the ZIP is protected with it.

Open the file with Unlock PDF, type the password once, and download a copy without it.