From the NetBeans wiki: “You can run NetBeans with the --fontsize <size> option. The default <size> value is 11. You can set it to 12 or even a higher value and see if it works better for you. The --fontsize argument applies to fonts used in menus, dialogs and most components in the IDE.”
For more details see:
http://wiki.netbeans.org/FaqFontSize