How to change the mailing label font
First, generate the mailing labels you need. For instructions on printing reports, see How to View, Print, and Save Reports.
When you are on the print preview screen, in the upper right corner, choose RTF where it says PDF, then click the blue disk icon (Save).
Open the saved report in MS Word.
Use Ctrl + A to select all text and change the text up to size 10, or maybe 11 font, but not 12 (because that's too big to print with the proper formatting).
Print the labels from MS Word.