If you make a duplicate copy of your file, it will contain duplicate account information. You can then delete tables, layouts etc from this copy to discard what you don't want and can then add or import tables, scripts etc to create your new file with identical accounts.
You may also want to investigate scripts for keeping the account info in two or more files properly in sync. (This can be used, for example so that a user can change their password and make identical updates to their password in every file in the system.
You may also want to research server side authentication as an alternative approach to managing user access.