The font size can be changed by the Font Size drop list on the Status Bar. The font size is scaled along with everything else on the layout so text is always the same relative size as other layout objects.
The font can be selected by the Font Selection dialog invoked by the Options|Fonts ... menu item or by Shift-Right-Click.
You can use the Describe command to modify the contents of existing Text objects.
Note: loading fonts (or changing sizes) can take a noticeable amount of time.