Is it rude to ask for copies of your reference letters?

So I have an interview coming up and the employer asks for reference letters from clinical instructors. I asked all of my clinical instructors to write me a reference letter. The employer said that they did not have to be confidential or sealed in an envelope or what not but my clinical instructors opted to mail them instead of me picking the letters up. Would it be rude to ask the employer for a copy of my reference letters they recieved? I mean they are my reference letters and they did not have to be confidential. And I would need them for future interviews as well. Would the employer look down on that??