The Minimum/Maximum Quantities extension for WooCommerce allows you to define minimum and maximum allowable product quantities per product, order or variation. It also lets you define a group quantity if your product must be bought in groups of x.
WooCommerce - Payment Gateway Discount and Fees extension for WooCommerce allows you to define discount or fees for all payment gateways. On checkout discount or fees will be applied based on choosen payment gateway.
Easy Digital Downloads - Download of the Day allows you to promote you downloads/items every day by showing them to your customer in a handy widget. Add a widget that shows the downloads of your choice as the downloads of the day.
The Dropbox extension for Easy Digital Downloads gives you the power and ease of use of serving your downloadable products through the Dropbox infrastructure. Easily choose a file from your Dropbox account via the Choose from Dropbox button and the plugin will do the rest.