Protect PDF
Lock a PDF with a password using AES-256 encryption, without uploading it.
Real Encryption, Not Just A Lock Icon
A password on a PDF is only as good as the encryption behind it. This tool uses the strongest a PDF can carry — AES-256 under the PDF 2.0 security handler, the setting Acrobat calls “Acrobat X and later” — and encrypts every piece of text, every image and the document’s metadata, so nothing in the file can be read without the password.
Most online PDF protectors ask you to upload the very document you want to keep private. Here the encryption happens in your browser with its built-in cryptography; the file is never sent anywhere. Bookmarks, links and form fields come through intact.
Key features
- AES-256 encryption — PDF 2.0 standard security, revision 6.
- Everything encrypted — text, images, fonts and metadata, not just a flag.
- Optional permissions — printing, copying, editing, commenting and page assembly.
- Structure preserved — bookmarks, links, forms and document information stay.
- Never uploaded — the key is derived and the file encrypted on your device.
This tool runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
How to use: Protect PDF
- Drop in the PDF
Any unprotected PDF; the original on disk is not changed. - Choose a strong password
Type it twice. A passphrase of four unrelated words is ideal. - Set permissions if you want them
Open the permissions panel to restrict printing, copying or editing. - Protect and download
Open the new file once with the password to check it before sharing.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
Which PDF readers can open it?
Any reader from the last decade: Adobe Acrobat and Reader X or later, Chrome, Edge, Firefox, macOS Preview, and the PDF viewers on iOS and Android. Very old software from before 2010 may not support AES-256.
What happens if I forget the password?
The file cannot be opened. There is no recovery or back door — that is what makes the encryption meaningful. Keep the unprotected original somewhere safe, or store the password in a password manager.
Do the permissions really stop people printing or copying?
They stop reader software that honours them, which includes Acrobat and most mainstream viewers. They are not encryption, though: someone who can open the file with the password and uses a tool that ignores permissions can still print it. The open password is the real protection.
Does it work on digitally signed PDFs?
It will encrypt them, but rewriting the file invalidates an existing digital signature. Protect the document first and sign it afterwards, or share signed documents another way.
Why is the protected file a slightly different size?
Every encrypted string and stream gains a small random starting block, and the file is rewritten with its objects laid out plainly. The difference is usually a few kilobytes.