Hello everyone. I just wanted to let you know that I've provided a solution to this problem a while ago. Instructions are available here: http://onat.me/readonlymaker
If you want to learn more, I have some more comments in this thread, a little old by now but this solution still works, there actually are a quite a number of users.
It doesn't need anything to use, you just add "readonly" as a tag to a note, and they're locked in evernote in next sync, simple as that, works in every platform.
Best,
Onat
If you have any feedback, kindly reach out via evernote certified consultants page ( https://evernote.com/certified-consultants ) by searching with my name or via my website .