I think that's called a PDF. Not only does it lock the format, but it is also a format with a history of longevity and portability that survives multiple software updates better than file formats for most notation software products.

Yes your right about that. I'm writing when you go back to the score in Finale. You want to listen, checkup on something. When you have the score open. Even if finale asks you do you want to save, at the end of session you could click don't save. Even though I believe it an important feature first before you finish you see changes were made, you begin to fix it. Or people out of habit always press ok on the save before the end a session.

And for some reason, I find it easier to spot my mistakes in a black and white PDF, rather than on my Finale score with black, red, green, etc., markings.

There might be some merit to the request. Kind of like in Excel where you can ""Password Protect" a sheet from being ruined by the slip of the hand. Perhaps, like the copy filter, the user could lock/protect certain elements (or all elements) in a score. For instance, say you could lock note entry preventing changes to the notes on the page while still being able to edit slurs, expressions, etc.

Just an idea.

You can do this already in Finale, even though it's not called locking a score.

1. Lock all systems

2. In preferences/edit, uncheck the automatic settings, click apply, done.

I can open any file and nothing will change. The only exception being, if I open an older file with a newer version of Finale, due to changes in the program, elements might change in this circumstance.