Protect PDF
Lock a document with a password.
Drop your PDF hereor click to browsePDF only, up to 250 MB each.
Files stay in your browser. Nothing is uploaded.
What this tool does
Encrypts a document with AES-256 so it cannot be opened without the password. The strength is not a choice — it is always 256-bit, because the older 40- and 128-bit modes are broken. The password is typed twice and never leaves the tab, and there is no way back: a file locked with a password nobody remembers stays closed.
How to use it
- Drop the PDF.
- Type the password to open the document, then repeat it in the second field.
- Under What others may do, decide whether printing, copying, changing the content and adding comments stay allowed.
- Download the protected file.
Common questions
- What happens if I forget the password?
- The document stays closed. Nothing is stored here and there is no reset link or recovery code, so write the password down somewhere safe before you run the tool.
- Can I pick a weaker encryption for an old reader?
- No. Every file is written with AES-256. The 40- and 128-bit modes some old readers expect have been broken for years, so offering them would only make a bad answer possible.
- Do the permission checkboxes really stop anyone?
- Not on their own. Permissions are a request the reader software is free to ignore; the password is the part that actually keeps the document closed.