Protect PDF
WEBAdd a password and permission controls to a PDF with real AES-256 encryption — free and right in your browser. Nothing is uploaded.
What is the Protect PDF tool?
Protect PDF adds a real password to a PDF file — not a cosmetic lock, but genuine AES-256 encryption applied to the document itself, so it can't be opened without the password in any PDF reader. The whole process runs inside your browser: the file and the password you set never travel to a server, unlike most online PDF protection tools that upload your document to encrypt it remotely.
Set an open password so only people who know it can view the file, and optionally set permission controls separately — restrict printing, copying or editing even for people who do have the password, useful for contracts and reports you want read-only. Because the encryption happens on-device, there is nothing to trust beyond your own browser: no storage policy to read, no account, and no watermark on the protected file.
It works the same on a phone as on a desktop — open the page, add your PDF, set a password, and download the protected file straight to your device, ready to send to whoever needs it.
How to use the Protect PDF
- Open the PDF you want to protect — drag it in, pick it from your device, or choose a recent file.
- Enter the password you want to set as the open password.
- Adjust permission controls if needed — printing, copying or editing.
- Export the protected PDF — the encryption happens right in your browser; nothing is uploaded.
- Download the password-protected file and share it with whoever needs the password.
Frequently asked questions
Is it safe to password protect a PDF online?
Yes — with Carbide, the encryption runs entirely in your browser, so the password you set and the document itself are never transmitted anywhere. Upload-based tools have to send your file to their servers to encrypt it; here there is nothing sent in the first place.
What encryption does this use?
Real AES-256 — the same modern encryption standard used by password managers and secure messaging apps, applied directly to the PDF's structure so any compliant PDF reader will ask for the password before opening it.
Can I stop people from printing or copying text, even with the password?
Yes. Permission controls are separate from the open password — you can allow someone to open and read the file while restricting printing, copying or editing, useful for documents you want to stay read-only.
Will I need this password to open the file myself later?
Yes — once a PDF is encrypted with an open password, every PDF reader will ask for it, including your own. Keep it somewhere safe; there's no way to recover a forgotten password without it.
What's the difference between this and Unlock PDF?
Protect PDF adds a password to a file that doesn't have one yet. Unlock PDF does the reverse — it removes a password from a file you already have the password for.