Depends on which program you have. In SongWriter and above, there will be a command "Fit Music" (or Fit Measures, depending on the year version) that will allow you to set the number of measures per line. You will need to look in your help files, to find out exactly where this command lurks.
NotePad does not have this option.
PrintMusic 2004, 2006, 2008, 2009, 2010; Finale 2010b, 2011b, 2012c
Windows XP, Mac OS 10.7.4