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Protect PDF
Lock with a password. Free, no sign-up.
or drop it here
Protect PDF runs inside your browser — your file never reaches our servers.
How to protect PDF
Protection encrypts the document. Without the password the file cannot be opened — by anyone, including us.
- Select your PDF. Any document.
- Set a password. Optionally also block printing, copying or editing.
- Download. The encrypted copy. Your original stays as it was.
AES-256, whatever version your PDF claims to be
The library underneath picks its cipher from the version number in the PDF's own header: a file that declares 1.4 — which is what a great many Word and LibreOffice exports declare — would be encrypted with RC4, broken long ago. Folia rewrites the header to 1.7 extension level 3 before encrypting, so every file leaves here with AES-256 regardless of what it arrived as. Nothing is re-rendered and nothing is re-compressed on the way through: the pages, fonts and images are the ones you started with.
The three tick-boxes are a different mechanism. They set permission flags carried inside the encrypted file, and those bind only readers that choose to honour them. Prevent editing also switches off form filling, annotating and page assembly; prevent copying also switches off the text extraction a screen reader relies on. This page uses the one password you type as both the open password and the owner password, so anyone you hand the file to can clear the restrictions as well as open it. Treat the password as the real lock and the flags as instructions to well-behaved software.
Encrypt last, after everything else is done
An encrypted PDF cannot be parsed, so the rest of the site stops at the door: Compress PDF, OCR PDF and the converters refuse and name Unlock PDF as the fix. This tool will not take one either — feeding an already-protected file back in fails rather than re-encrypting it. Do the visible work first: watermark, page numbers, compression, and encrypt the finished document as the final step. To change a password, unlock with the old one and protect again with the new one.
A password controls who opens the document, not what is inside it. Everyone you give it to sees everything, including whatever a black rectangle appears to be covering. If a name or a figure must not reach the reader at all, take it out with Redact PDF and encrypt afterwards.
Questions
What happens if I forget the password?
The file is unrecoverable. That is not a policy we could change — the document is genuinely encrypted, so there is no master key and no reset. Store the password somewhere safe before you close this tab.
Is this real encryption or just a restriction flag?
Real AES encryption. Some tools only set a "please do not print" flag that any reader can ignore; an open password here actually encrypts the content.
Does the password reach your servers?
No. Encryption happens in your browser, so the password never leaves your device — there is nowhere for us to store it even if we wanted to.
Can I set one password for opening and a different one for editing?
Not on this page. The password you type is used as both the open password and the owner password, so a reader who can open the file can also clear the printing, copying and editing restrictions. Those restrictions still have to be carried by encryption — there is no way to enforce them on an unencrypted PDF, which is why a password is required before the tick-boxes do anything.
Which readers can open an AES-256 protected PDF?
The file is written with AES-256 (V5, revision 5). Acrobat 9 and later, Apple Preview and the viewers built into Chrome, Edge and Firefox all open it, as do the common mobile readers. Software older than that predates AES-256 in PDF entirely, and refuses the file rather than prompting for the password.
Does protecting a PDF change its quality or size?
No page is re-rendered, so the text, images and fonts are exactly what you started with and nothing is downsampled. The file is re-saved on the way out, so its size can move a little in either direction — that is the re-save, not a change in quality.
Are my files uploaded to a server?
No. Every tool on this site runs inside your browser, using the same engine as the Folia desktop app. Your file is read from your disk into your browser’s memory, processed there, and handed back as a download. It never crosses the internet, so there is nothing for us to store, leak or hand over.
Is there a file size limit?
We impose none. The only ceiling is your own device’s memory, which differs from one computer to another — so we read what your browser reports about this machine and show the resulting limit on the page. Light tools like merge and rotate handle far more than heavy ones like OCR, which must render every page. For anything larger, Folia for Desktop has no limit at all.
Is it really free? Do I need an account?
Yes, and no. Every tool is free and unlimited, with no watermark and no sign-up. Ads pay for the site, and your own computer does the work, which costs us nothing. Signing in with a paid Folia plan simply removes the ads.