Can you add an existing local user to a domain

Hi, I have just created a new domain network in our office. Previously we were using a home network. Is there a way that I can get each existing user profile to connect to the domain? I dont want to creat a new user and such and not be able to use the current users my docs and email accounts. Also, a lot of the users here travel a lot so they need to access the same MS Outlook profile whether in the office or on the road. Thanks.