If a PDF contains sensitive information — a contract, bank statement or ID — you can lock it with a password so only people who know it can open the file. Here is how to add 256-bit encryption to a PDF online for free.
The tool applies strong 256-bit AES encryption on a secure server, and the file is deleted right after processing. Choose a password you will remember — without it, the PDF cannot be opened, and there is no recovery. Store the password somewhere safe.
How strong is the encryption?
It uses 256-bit AES, the same standard used by professional PDF software.
Can I remove the password later?
Yes — use the Unlock PDF tool with the current password to remove it.
Ready to go? Open the free Protect PDF tool — no signup, no watermark, and your files stay private. Browse all 140 free tools or read more on the blog.