Print the current file by pressing Ctrl+P, clicking , or by executing the File->Print menu command. Edit->Preferences selects which cards to print (all, tagged or just the active card) and the font to print in.
If you want to use fancy printing options beyond what ScrapBook offers, save to a text file (File->Text Files->Write Text File, F8) and open the saved text file in a word processor. Between each card is "—————————————". Change it to something else if desired, then format and print.