Yes, you need prepare at least 10 copies if you want to apply 10 schools.
BTW, PS and essay are quite personal issue. There are some principles, however, there is no universal templet for them. Both of them highly depend on your personal working experience, your goals (long-term and short-term), your personality, and your background, especially for B-school applicants. I think this may be the reason that there are not a lot of people here to discuss the detail of PS and essays. | 
