How can I change default font family in WireframePro?

To change font family of a component, follow the below steps:.

Select any component that has text like Button, Label, Text,..
In its component settings, select 'Font' to bring up the 'Font chooser' dialog box

In the font dialog box, select from built-in fonts / Google fonts to change the 'font family' of a component

To change the 'font family' of another component to already used 'Font' , select the 'Used' tab in the font dialog box. This helps to select fonts only used already in that project.