For some routes Interrail can only issue reservations on paper.

Which route are you trying to make a reservation for? If it is a route starting or ending in Spain, then you just call RENFE and collect the reservation within 3 days at a Spanish railway station.

I want one from Bucarest to Budapest, but it doesn’t make sense that you have to delivery and pay 9 euros extra and wait for 3 weeks...

you should be able to print it at home, other travels, same cities, you can print it at home….

If you ask a new question where you write exactly what reservation  (date, time and route) you want to make, you will get advice from some of the experienced travellers who are good at reservations. 

AND-senorita-IF you had just taken the few MIns to read the link on howtodo Yourself the RES you would have found the answer and would not have to fill even more cyberspace with useless complaints. To the utter surprise of all new youngsters only knowing their fones-many railways are still very old-fashioned and want you to some to their offices in estaciones.