How It Works
Upload / Input
Select your files or paste your content to get started.
Process
The work happens in this browser tab. Your file never leaves your device, so nothing is queued, stored or transmitted.
Download / Result
Get your results instantly. Download files or copy output in one click.
Features
How to use Protect PDF
Add the PDF
Drop in the document you want to secure. Encryption is applied in your browser.
Set a password
Use something long rather than something complicated — a passphrase of several words beats a short string of symbols.
Apply protection
The document is re-saved encrypted with a 128-bit RC4 key. Anyone opening it will be prompted for the password.
Test it, then share the password separately
Reopen the file to confirm the password works, and never send the password in the same message as the document.
When to use Protect PDF
- Emailing a document containing personal or financial details
- Sharing HR or medical paperwork that must not be readable if forwarded
- Protecting a contract draft before sending it to a third party
- Adding a basic access barrier to a file stored in shared cloud storage
FAQ
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About Protect PDF
Password-protecting a PDF encrypts its contents so the file is unreadable without the password. This is genuine encryption, not a display trick — the page contents on disk really are scrambled, and a reader that ignores permissions still cannot show you anything.
The cipher is worth naming, because most tools are vague about it. This one writes the PDF standard security handler with a 128-bit RC4 key. That is the format every PDF reader has understood since Acrobat 5, which is why the protected file opens everywhere — but RC4 is an old algorithm, and a determined attacker who has the file and the right software is not stopped by it the way AES-256 would stop them. It is the right tool for keeping a document away from someone who should not casually read it. It is the wrong tool for material that would cause real harm if it were broken; encrypt the container rather than the document for that.
It is worth being clear about what this does and does not protect against. A password stops someone who has the file from reading it. It does nothing once you have given a legitimate recipient the password, because from that point they can save an unprotected copy. Treat it as protection in transit and at rest, not as a control on what the recipient does afterwards.
The other thing to understand is that there is no recovery. There is no reset link and no support queue that can unlock the file for you — that is the entire point of encryption. If you forget the password on the only copy of a document, it is gone. Record it in a password manager before you close the tab.
Tips and limits
- A four-word passphrase is both stronger and easier to remember than a short password full of symbols.
- Never send the password in the same email as the file — use a different channel entirely.
- There is no recovery. Save the password in a password manager before closing the page.
- Encryption protects the file, not the recipient's behaviour. They can always save an unprotected copy once they can open it.
- The cipher is 128-bit RC4, not AES-256. Good against casual access; not against a determined attacker who has the file.
- One password does both jobs here — it opens the document and owns its permissions. There is no separate owner password.
- Keep an unprotected original somewhere safe, or you will eventually lock yourself out of your own document.