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Protect PDF

Add a password to a PDF, encrypted with AES-256.

Select a PDF to protect

Click to choose, or drop a file here

Related PDF tools

Fill & Sign PDFFill in a PDF form and sign it — type text, tick boxes, add dates, drop your signature and initials anywhere.Sign PDFDraw or type a signature and place it on the page.Redact PDFBlack out and permanently flatten sensitive areas.Unlock PDFRemove a known password from a PDF.

Linda PDF — frequently asked questions

What encryption does this actually use?+

AES-256, the current PDF encryption standard — the same class of encryption Adobe Acrobat and other professional tools use, applied entirely in your browser via the Web Crypto API.

Can I recover the password if I forget it?+

No — there's no recovery mechanism, by design. That's what makes the encryption real. Keep the password somewhere safe; if it's lost, the file can't be opened by anyone, including you.

Do you upload my files to a server?+

No — every tool here processes your files entirely on your device, and nothing is uploaded to a server. The AI tools that used to send extracted text to a server are currently disabled.

Is there a file size limit?+

There's no artificial limit we impose, but since processing happens in your browser, very large files (500+ MB or 1,000+ pages) are limited by your device's memory rather than by us.

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