You can also get your Geocoin at the Tourist Info in Paderborn (Marienplatz 2a, 33098 Paderborn). Just bring your completed hiking pass with you and prove with seven stamps that you have hiked seven rounds. Then you can receive your reward personally and take it home with you.
PS: It is worth taking a look at the listing of Pinboard Paderborn (GCQCZN) before your visit. 😉
Tourist Info Paderborn