Since each Mileage Book account represents one individual driving account, it is not possible to have more users in one Free, Pro or Pro+ account. However, it is possible to use one account if you just have to keep track of one car, for example a company car that is being used by more employees.
Here you use one shared account, for example, to keep track of how many kilometers/miles your company car has driven.
It works by all users downloads the Mileage Book app on their mobile device and then signing in with a shared account.
If you are looking for a multi-user solution to keep track of each employees' individual driving accounts, you should look at an Enterprise or Business solution.