How to password-protect a PDF with OnyxPDF
- Drop your PDF into the tool.
- Set an open password (and, if you want, a separate owner password for permissions).
- Choose the permissions: allow or block printing, copying and modifying.
- Click “Protect & Save” and download the encrypted PDF.
Why do it in your browser instead of uploading?
- Real encryption, not a fake viewer lock: AES-256 via qpdf, the same engine class used by desktop tools.
- No upload — the unencrypted original never leaves your device, which matters when the document is sensitive enough to encrypt.
- Full permission controls (print / copy / modify / annotate) like paid tools offer.
- Free and unlimited; several big sites reserve permission controls for premium tiers.
Good to know (honest limits)
- If you forget the password, the file cannot be recovered — by anyone, including us. Store it somewhere safe.
- Encryption protects the file at rest; once a recipient opens it with the password, they can share screenshots or copies — permissions reduce casual misuse, they are not DRM.
Frequently asked questions
What encryption does this use?
AES-256 (with AES-128 also available) applied by qpdf running as WebAssembly in your browser — the same standard desktop PDF tools use.
What is the difference between the user and owner password?
The user (open) password is needed to view the file. The owner password controls the permission flags (printing, copying, editing). Set both for the strongest result.
Can I remove the password later?
Yes — with the Unlock PDF tool on this site, as long as you know the password.
Is my PDF uploaded to be encrypted?
No. Encryption happens locally; uploading a sensitive file to encrypt it elsewhere would defeat the purpose.