Because each voucher can be used multiple times up until their specified value its important to keep track of what its being used for. Each time a voucher is used you can track the corresponding order its been used on, the amount and date.
We've got lots of template examples to get you started, walking you through the process. We've even thrown in some PDF example templates to get you started!
See our Templating Documentation
Available for Craft 2 for $99, trial locally for as long as you need.