I have a MacBook Air, 13-inch, Mid 2011, running Mac OS X Lion 10.7.5. I intend to have a dual boot setup with Ubuntu 13. So I did some googling and found the some instructions (http://nosemaj.org/dual-boot-mac-linux). However, when I tried to resize the OSX partition, I found no option in Disk Utility to do that. Is it because the author was running a different version of OS X?
OSX Disk Utility hasn't really changed much in years, outside of a few features (new format handling, etc.) - it's basically the same now as it was around 8 yrs ago.
There isn't really a "change size" button, instead it's a slider:
[moved to an answer]