With this plugin, your players won't be able to see your plugins by using /pl or /plugins, unless they have a certain permission. This plugins also has a configuration option to block /? and /help, which show your plugins.
The /?, /help and /pl or /plugins already exist, so the plugin itself only creates one command in the game:
This plugin is easy to install, just stop your server, place the plugin jar file in your "plugins" folder, and start your server again! You'll see that the folder for the plugin will be generated, as well as the config.yml!
Open the configuration file, and you will see different annotations. Each one explains fully each option. Modify the config as you wish, and if your server is online, use /pluginhider reload, otherwise, just start your server. After that, you're done!