For which train exactly? There may be alternative ways of booking but then we need to know which train.

As a very general rule: do not worry too much about getting these REServations monthes advance (as so many a newbee seems to think), often it is not even possible that long. The system is basically still as it was for over a century: you do that at a counter in a real station-and that often does not even has to be inside the country where you use that train. And then you get that paper-where often noone seems interested in anymore (conductors want to see the TIcket=on your fone or in paper).

Most cases where those papers are needed are INTernat. to/fro France and In and to/fro ESpana=Spain. But without exact detials impossibel to tell.

Hello, thanks for your help so far. The trip starts on June 22nd in Split, connects in Zagreb, and ends in Zurich. Both the Split-Zagreb and Zagreb-Zurich require reservation and both are printed tickets. Prior to the 22nd I will be in Split from the 18th-22nd and prior to the 18th I will be in Athens from the 10th-18th. Any tips?

You didn't say which train from Split to Zagreb but it looks like you'll be taking the day train leaving Split at 8:31. In that case, just buy the seat reservation on your first day in Split, from the ticket office. A seat reservation from the Croatian ticket office is HRK 8 (~EUR 1.07), which is only a fraction of the price Eurail want. A few days in advance shouldn’t be a problem, especially since this is in the middle of the week.

For the night train Zagreb - Zürich, you can do that online on the ÖBB website, using these steps. Seat = 14 €, couchette from 34 €, sleeper from 54 €. You'll get a PDF to print. For night trains, it is wise to book some time in advance.

Thank you so much!! That helps a ton.