I have a manuscript ready for submission. However, I would like to send it to some other doctoral students in my country for them to proofread. These two persons are not my friends, we met on a conference and I surely do not trust them ethically, as we have not worked together before. I have heard a lot of stories about people stealing other's works, and I don't want to get scammed.

How should I approach the situation? Is there any way I can claim copyright over a manuscript?