Shiptheory sends through the electronic customs data to Deutsche Post when the shipment is booked in. This means that you do not need to print off a commercial invoice to send a shipment internationally. The only thing you'll need to do is ensure your product data is being sent to Shiptheory from your channel.
If you have any questions about this or need help setting up your product data to be sent through to Shiptheory, feel free to contact support and we'll be happy to help.