Protect a PDF with a password, free, in your browser
A password to open the file, an owner password for the restrictions, and what a reader may do: print, copy, change, annotate. AES-256, and the password never leaves this tab.
✓ no upload✓ AES-256✓ password stays here✓ works offline
How protecting works here
- Drop the file. The PDF opens in a worker in your tab.
- Set the passwords and permissions. A password to open, an owner password that lifts the restrictions (or leave it empty to use the same one), and the four permissions.
- Download. Every string and stream in the file is encrypted with AES-256 and a key derived from the password by the standard's own hash. The result is opened again with the password to check it before the download.
What it does
- Encrypts with the current standard (AES-256, revision 6), which every modern viewer reads.
- Keeps the passwords in this tab only; nothing is stored, nothing is sent.
- Sets restrictions that viewers enforce without the owner password.
- Lets you restrict without a password to open: an owner password alone.
What it does not do
- It does not make a file that a determined person with the right tools cannot open; restrictions are a request to the viewer, and only the open password is real protection.
- It does not sign the document; signing is a different thing, done by Sign PDF.
- Restrictions do not hold against someone who has the password to open, unless the owner password is a different one.
Questions
What is the difference between the two passwords?
The password to open is needed to read the file at all. The owner password lifts the restrictions (print, copy, change). Leave the owner password empty and both are the same.
Is AES-256 the same as what Acrobat uses?
Yes. It is the standard security handler at revision 6 from the PDF 2.0 specification, which Acrobat has written since version X.
Can someone remove the restrictions?
Restrictions are enforced by the viewer, not by the encryption, so any tool can remove them, including this site's Unlock. Only the password to open keeps the content private.
Where does my password go?
Nowhere. It is turned into a key inside the worker in your tab and discarded when the job is done. The site has no server that could receive it.
Does my file leave my computer?
No. Everything runs in your browser tab. The only network requests are the site's own files.
Guides for this tool
- PDF privacy and protection: the complete guideWhat a PDF password really protects, how true redaction works, what metadata leaks, and how to send files safely.
- Add a DRAFT watermark to a PDF, one that shows on screen and on paperAdd a DRAFT or CONFIDENTIAL watermark to a PDF that shows on screen and on paper.
- Save an email or a whole thread as a PDF, attachments includedSave an email or a whole thread as a PDF in Gmail or Outlook for records or disputes.
- Fill out a W-9 as a PDF, free, without your tax number leaving your deviceFill out a W-9 free without uploading your tax number: the IRS PDF has real fields.
- GDPR and online PDF tools: what is allowed at work, in plain wordsGDPR and online PDF tools: uploading a client PDF to a converter is processing personal data.
- How strong is PDF encryption? AES-256, older schemes and the passwordAES-256 in current PDFs cannot be broken by trying keys; the password is the weak point.