While it isn't the most powerful image editor available, it offers a sufficiently broad range of tools, without becoming too overpowering. However, there are a few basic omissions from the feature set of Paint.NET that do slightly undermine the package as a whole and one of these is the inability to edit text after it has been added to an image.
Thanks to the hard work and generosity of Simon Brown, you can download a free plugin from his site that allows you to add the ability to have editable text in Paint.NET. At this point I should clarify that while this article is only concerned with the editable text plugin, it is now part of a pack of plugins that offer some other useful functionality to Paint.NET, so you're actually downloading a number of plugins in a single ZIP package.
If you've not already got a copy of Paint.NET, you'll need to download a free copy of that and install it on your PC. You can find out a bit more about Paint.NET in our review of the application and you'll also find a link to the download page there too.
The following pages will show you how to install the plugin and then how to use it so that you can edit text in Paint.NET.