You can say both "Turn the page" and "Turn the page over."

I would say "turn the page" for a book or magazine (something where the pages are all connected together). I would say "turn the paper over" or "turn over the paper" if it is one individual piece of paper. For example, "Please answer the questions on this form. Be sure to turn the paper over because there are more questions on the other side."

I think Turn over...