I looked up this thread because my script was shrinking to such a small size that I had trouble reading it. While the answer above will work to a degree, the issue is actually one of Windows, at least when you are using a PC. It turns out that in Windows you can increase or decrease the font size in any window by clicking in the window to select it, then holding down the Ctrl key and using the scroll wheel on your mouse. If you don't have a scroll wheel, I suspect that other mouse actions can also be used.
My problem with the shrinking is one that I haven't quite figured out, but I believe it is the same trigger, but this happens on a laptop when my hand goes over the mouse keypad and some other buttons are pressed. It's specific to particular laptop keyboard designs. It's frustrating, but the CTRL-Scroll does get the text size up or down very easily.