This is no problem at all!
If you do not have the possibility to print the return documents, use the following option:
Use the QR code!
In addition to the actual return label, you will also find a so-called QR code on the return documents. This is located on the left side, which has the heading "Shipment information for your documents".
Germany:
Show this QR code on your smartphone at a DHL branch, a parcel store, at your parcel delivery service or at a DHL Packstation. DHL will print out the label for you. Please carefully remove old shipping labels and barcodes beforehand.
Austria:
Simply show the QR code on your smartphone at the Post AT branch counter or print the label at the franking machine in the self-service zone.