You are not supposed to need a printed invoice since the order is PLT (paperless trade) which means that all the information DHL needs is already in their system. The invoice they are asking for is available digitally for them. However it seems like DHL offices and partners do not always know about this system. If they insist after you inform them that the shipment is PLT and it is not required, please contact us and we can email you a return invoice to use. Apologies for any inconvenience this causes.