If you want to send documents by mail to a customer, you can set this separately for each customer in billwerk. Current prices for sending letters can be found here.
For configuration, select the customer under "Customer > Name":
You will be redirected to the customer details. Select the editing function here:
Here you can now select the "Letter" shipping method under Options. Please note that the "Letter" option can only be selected if address data is stored for the customer. Similarly, "E-mail" can only be selected if an e-mail address is available for the customer.
Don't forget to save the changes at the end.