About Protect PDF
Protect PDF adds a password to your document so it can't be opened without it. Encryption happens in your browser using 128-bit RC4, a standard supported by every PDF reader, so neither the file nor the password is uploaded.
How to use Protect PDF
- Select the PDF you want to protect.
- Enter a password and repeat it to confirm.
- Select Protect PDF and download the encrypted copy.
What to check
Choose a long, unique passphrase and store it in a password manager — a lost password cannot be recovered. Send the password through a different channel from the file. For stronger confidentiality of specific details, remove them first with Redact PDF.
Limitations
128-bit RC4 keeps casual readers out but is older than AES encryption; use dedicated software for highly sensitive material. Already-encrypted PDFs must be unlocked first with Unlock PDF.
Frequently asked questions
Does a password stop people copying my content?
No. Anyone who can open the file can still see and capture its contents. Encryption controls who can open it.
What if I forget the password?
It cannot be recovered. Keep a copy of the unprotected original somewhere safe.
Is my file uploaded to protect it?
No. The encryption runs entirely in your browser.