booking prague-berlin train ticket online

On the German Rail site you can print tickets for Berlin-Prague but not for Prague-Berlin. That's because the conductors in Prague don't have the right hand-held devices to scan self-printed tickets. If you choose to have the tickets mailed to you, they will be standard paper tickets. You can try the Czech Railways site, but I don't know if the site allows for printing tickets yourself.

I don't think the Czech Railway site will sell tickets for travel outside the CR. They don't show prices online. You still have plenty of time for the tickets to be delivered by mail. Another option would be to buy the ticket online from the Bahn for Bad Schandau, the first stop in Germany for that EC, to Berlin. With a Saving Fare, the price should be no more than Prague to Berlin. You can print that ticket online. In Prague buy a ticket for the same train to Bad Schandau. In May, I bought a ticket from Prague to Bad Schandau at the Prague station for 357 Kc (the equivalent of €14,28) for one person. It was a little less in Euro, but I had Czech Koruna to get rid of. I was able to find an unreserved seat, but you could also get a reserved seat when you buy the ticket. You don't have to get off the train in Bad Schandau (but it's a nice place to spend a few days); you just start using the other ticket there.

Yes, you absolutely should go to the Czech site (www.cd.cz). Look under eshop. I bought (and printed) prague to berlin tickets from there in April. Used them in May with no problems.

Thanks for all of the help!