If you sell digital products such as WordPress plugins and themes, you agree with me that Easy Digital Downloads (simply EDD) plugin is arguably the best to set up a store for selling.
I use it in selling my premium plugins and couldn’t be happier.
A month ago, I release an extension for EDD called License Free Download that allow shop owners to give free downloads to customers that holds a license for another product.
We use the plugin extensively over at ProfilePress store to offer certain themes and extensions for free to customers who bought the main plugin.
How it Works
For example, you could make Product C and D free to customers that bought product A and B. All that is required from them to get the product for free is for them to enter their license key of product A or B in a form displayed using the shortcode [edd_lfd].
On successful license authentication, the price of C or D (whichever they are trying to get for free) will be set to zero (0) thus enabling them to get the product for free.
If the customer or user checkout with just the free product in cart, they won’t have to go through the store payment gateway to get the product. Instead, they will be redirected to order confirmation page where they can download the free product.
Should in case they added a paid product to the cart containing the free downloadable product, they will have to pay for just the other product with the free download fee set to zero.
For more information, see the plugin documentation.