This is a first approach to add paragraph numbering to CKEDitor.

There are some known issues:
 - The content is autoresized. Yet there is no option to fix editor's height and make number bar scrolling
 - requires jQuery
 - requires AutoGrow plugin

To install it for your CKEditor instance create a directory in CKEditor plugins directory named whatever you want (i.e. linenumbers) and put plugin.js to it.
In config.js add 'linenumbers' (or your name) to config.extraPlugins string.