Protect PDF
Drop a PDF, set a password, optionally restrict actions, then download. Your file never leaves your device.
How it works
- Drop a PDF into the upload area. The original is never modified.
- Enter a password. Use a long, hard-to-guess passphrase — that's what actually protects the file.
- Confirm the password to catch typos.
- Optionally restrict actions: forbid printing, editing, copying, or annotations. Leave all checked to just add the password without restrictions.
- Click 'Protect PDF' and download. The locked copy needs the password to open in any reader.
Frequently asked questions
What encryption algorithm is used?
AES-128 (PDF security handler revision 4, V=4). It's the Acrobat 7+ standard and what most modern PDFs use. With a strong password it's not crackable in practice.
How strong should my password be?
Long matters more than fancy. A four-word passphrase (e.g. 'glass.river.purple.kite') beats 'P@ssw0rd123' by a wide margin. Treat the file as effectively unrecoverable if you forget it — there's no backdoor.
What's the difference between user password and owner password?
User password = required to open the file. Owner password = required to remove the restrictions. We default to using the same value for both (simplest UX). Most PDF viewers enforce both transparently.
Does the permission checkbox actually prevent printing or copying?
It sets the standard PDF permission flags. Mainstream readers (Acrobat, Preview, browser viewers) honor them. Some niche tools can bypass them — never use these flags as a security boundary for genuinely sensitive content; encrypt with a strong password and don't share it.
Is my password sent anywhere?
No. Key derivation and AES encryption both run inside your browser tab. Your password is held in memory only for the duration of the operation.