Add additional fonts?
 

Im very interested in Omnigraffle for diagraming. I would use it for a bible study outline that uses greek fonts. Im using the trial and I dont see an option to add any additional fonts. Can this be done?

OmniGraffle uses the OS X font panel to select fonts. You would need to add them to your Font folders using e.g. Font Book so that they became available to your apps.

FWIW, the easiest way to input Greek characters is to activate the Greek keyboard in the International>Input Menu system preferences. Toggle to the Greek keyboard when you want Greek characters, then toggle back to your default keyboard when you need e.g. Roman characters.