I will quckly run through what you need to do to configured the editor to use custom font-sizes in the drop-down font combo in the toolbar. It really is quite simple. To do this we will need to add one parameter to the editor's 'config.js' file.

This is found by navigating to:-

plugins/editors/jckeditor/config.js

Then we need to define new font size by adding the parameter 'config.fontSize_sizes' to the config.js file as shown below:-

config.fontSize_sizes = '16/16px;24/24px;48/48px;';

Example:-

/*
Copyright (c) 2003-2010, CKSource - Frederico Knabben. All rights reserved.
For licensing, see LICENSE.html or http://ckeditor.com/license
*/

CKEDITOR.editorConfig = function( config )
{
    // Define changes to default configuration here. For example:
    // config.language = 'fr';
    // config.uiColor = '#AADC6E';
    config.fontSize_sizes = '16/16px;24/24px;48/48px';
};
CKEDITOR.version = '3.4.6';

    

For more info on this matter please see offical cksource documnetation.

• http://docs.cksource.com/ckeditor_api/symbols/CKEDITOR.config.html#.fontSize_sizes