Set an open password (required) and a permissions password (optional) on your PDF with 256-bit AES encryption. All encryption happens entirely in your browser — your file and passwords are never sent to a server.
First run downloads the engine (~4MB)
The permissions password controls changes such as printing and editing. Leave it blank to use the same value as the open password.
Upload a PDF, enter an open password, and press Apply to see the result here.