It has been a while since I used that one, but I seem to recall there was an issue about this. You should be able to print at the same font size you're using on screen, which makes it an easy adjustment.
Here's a clip from the Apple website:
By default, when you print a document, TextEdit places line breaks at the same places as they were on screen. If the lines are too long for the paper you’re printing on, TextEdit reduces the size of the font until the lines fit. For example, if the document window is very wide, TextEdit must reduce the font size until the lines fit.
You can have TextEdit keep the font size the same, and change the locations of the line breaks instead.
*To use the same font size in printed and onscreen documents:*
Choose Format > “Wrap to Page.” A rectangle shows the margins of the document in the window.