[Zubersoft]

I rely on Microsoft's model for UWP applications, which means the storage is set up per user. There is no way to install anything for all users. If you use the Microsoft Store version of MobileSheets, then you can install it for each user as long as that user's account has the ability to install the MobileSheets purchase (i.e. there is a purchase independently for each user or their accounts have shared purchases, i.e. family). If you use the FastSpring store version, I'm not sure if you'll be able to use the same license key for two users on the same machine. I'm not entirely sure I know which information the license software I'm relying on uses to uniquely identify the installation. 

Mike