Free Trial

Curious to how you could have a checkout that would enable 1 license for Free and then if they needed more, they could come back and purchase a package of say 10 but have that not generate a new license but instead apply it to their existing license?

Is this possible? I am trying to integrate this into an app and do not want the user to have to reconnect each time they upgrade to put the new licenses in.

Is there some sort a login the user gets where they can upgrade an existing license to a new package? Thanks for clarifying.