You can use a colored pen, such as blue (black is sometimes difficult to distinguish from the copy effect without careful inspection), and indicate in the eye-catching place of the original that this original is only for XX business use.

You can also use the chapter "The second copy is invalid". Financial personnel often use this chapter when dealing with business.

If the interviewer asks about the use of such copies during the interview, he can answer: "This just reflects my caution and carefulness". If the other party doesn't want to hire you because you made such remarks in the copy, I think that's just an excuse.