I am executing 'pastefromword' command on CONTROL + V key down. To achieve this I specified keystrokes config option as shown below.
var editor = CKEDITOR.replace( 'editor1', {dialog_backgroundCoverColor : '#A00000', keystrokes : [ [ CKEDITOR.CTRL + 86 /*V*/, 'pastefromword' ], [ CKEDITOR.ALT + 109 /*-*/, 'toolbarCollapse' ] ]});