Out of curiosity I tried to create a second user account and was able to do so. I simply created a new account and edited the profile for that account, using a different name than mine. I then went to the File drop down menu (where I created the new account) and chose Open Account, and opened my original one. I then checked my profile and everything was as I had left it. I don't know how many users you could add. Maybe contact support and find out?