I is possible to make Volume App Purchases – so you can buy license to an App at the Windows Store for Business and distribute it to your AzureAD users.
Windows Store for Business overview https://technet.microsoft.com/en-us/itpro/windows/whats-new/windows-store-for-business-overview?f=255&MSPPError=-2147217396
First sign in to your Windows Store for Business
Use your WsfB Admin account
Go to Settings –> Account information
Select Show my payment options
Add a new payment method
Enter your credit card information
Verify your Credit Card information is correct
Fin the App you want to buy
Select Buy now
Verify your information
Add the app to private store
In the private store you can now see the “Add in progress” – this can take up to 24 hours.
After that you can deploy the app to users from Windows Store for Business or from your management tools.