Welcome to the age of squint club
Unfortunetly there is no built in way in Aperture to do this as far as I am aware.
One thing I find useful is to zoom the screen when I need to se a particularly difficult bit of text. If you hold the control key down and scroll the mouse (if you have a magic mouse its a single swipe up) the sceen will zoom in to the cursor point. To get back to noraml just scroll in the oposite direction.
In addition to Frank's suggestions:
Experiment with turning off font smoothing with fonts below a set size. This helps some, and galls others. The setting is at "System Preferences→Appearance".
There are other zooming tools in addition to the "scroll to zoom". These are set at "System Preferences→Univarsal Access→Zoom→Options".
You might consider running your display at a smaller resolution (this will make the system fonts render larger). "System Preferences→Display".
If you are still unsatisfied, you probably can find a third-party utility to change the system font settings. (TinkerTool used to do this.) I advise against it, as it almost always leads to unintended consequences, and in addition is difficult to maintain through the many updates and upgrades.
You could make a feature request of Apple, via "Aperture→Provide Aperture Feedback". Even a "Small, Medium, Large" might be useful in the Library pane of the Inspector.
I use work bifocals with the "reading" lenses set specifically to the distance of a computer screen. Invaluable, imho.
Message was edited by: Kirby Krieger