Easy Digital Downloads Points and Rewards:
Easy Digital Download Points and Rewards extension allows you to reward your customers for purchases and other actions. They can then redeem these points for discounts on future purchases.
The number of points awarded per purchase can be configured globally, per category, and even per product. This gives you complete control over the reward system. Along with controlling the number of points awarded, you can set the amount that each point is worth. For example, one point could be equivalent to 1$ or 100 points could be equal to 1$, or any other ratio imaginable.
Customers can build up their point balance over time and then choose exactly when they wish to redeem those points for a discount. Store admins can easily manage the customer balance points via the backend.
Points and Rewards is an excellent extension for building a “store credit” type system. Want to reward customers for helping out in your support forums or for reporting a bug? You can simply give them some points that they can redeem on future purchases.