In Xodo Windows version 4.5.16, select "Save Copy", then "Encrypted"
Using Xodo Windows Subscription, select "Actions", then "Security" | "Encrypt"
Provide a password when prompted
The document will open in a new tab. To confirm that the password works, you can close the tab and re-open it.
The document will open in a new tab. To confirm that the password works, you can close the tab and re-open it.