To change the default font in the editor you can use cascading style sheets e.g.:

body { font-family:SansSerif; }

or / and:

p { font-family:SansSerif; }

For embedding CSS styles / stylesheets into the editor you could use the applet's setStyleSheet / setStyleSheetURL / addStyleSheet JavaScript API methods.

More details on these JavaScript APIs can be found within our Integration Manual at the chapter 'JavaScript API / Java API'.