Copy content of a locked file

I have a team of transcribers; I send them images, they send me back a locked WORD documents.
I CAN unlock it, but prefer not to.
But I need to COPY the content and past it into my own document.

"Locking"  should allow copying; it should only prevent changes.

BUT - sometimes Ctrl-A Ctrl-C in theirs and Ctrl-V in mine does work.

And sometimes it does not !

Q1: What am I doing wrong, and what am I doing right ?

Q2: If I have to unlock it, how do I re-lock it ?  
        Or does it stay locked if I don#t save it ?