function plt_hide_secure_downloads_menus() {
//Hide "Secure Downloads".
remove_menu_page('opsd');
//Hide "Secure Downloads → Secure Links".
remove_submenu_page('opsd', 'opsd');
//Hide "Secure Downloads → Files".
remove_submenu_page('opsd', 'opsd-files');
//Hide "Secure Downloads → Settings".
remove_submenu_page('opsd', 'opsd-settings');
}
add_action('admin_menu', 'plt_hide_secure_downloads_menus', 12);