Fubra

Steve

This plugin adds two areas of functionality: Global page, category or tag permalink structures and individual custom permalinks.
Options are added to the Permalinks Settings page allowing you to specify the structure for pages, categories, tags and authors.
By default – if custom permalinks are enabled – pages are accessible in the format <code>/page/</code> or <code>/parent/page/</code>.
You can modify this format in many different ways, for example:
<ul>
<li>Add an extension: <code>/%pagename%.html</code></li>
<li>Add a parent directory name: <code>/content/%pagename%/</code></li>
<li>Prefix the page name: <code>/page-%pagename%/</code></li>
<li>Or using a combination of the above.</li>
</ul>
This same format applies for categories, tags and authors, however the structure tokens differ:
<ul>
<li>Categories: <code>%category%</code> (E.g. <code>/category/%category%.html</code>)</li>
<li>Tags: <code>%post_tag%</code> (E.g. <code>/tag/%post_tag%.html</code>)</li>
<li>Authors: <code>%author%</code> (E.g. <code>/author/%author%.html</code>)</li>
</ul>
Each permalink base can be edited directly via these settings, for example using <code>/people/%author%.html</code> as the Author permalink structure will replace <code>/author/</code> with <code>/people/</code>.
If no prefix is found, permalinks will be prepended with a default (category, tag or author) – with the exception of pages.
Note: Ensure you have included the correct structure tag somewhere in the url.
Additionally, an option is added to the edit screen allow you to specify the permalink for an individual post or page.

Permalink Editor

Fully customise the permalink for an individual page or post and globally set the permalink structure for pages, categories, tags or authors.

wpyb

To prevent that usernames are publically visible, the username in the author’s permalink is replaced with the author’s ID. 
In case the page is invoked with the default permalink structure, it is displayed “Page not found”.
Additionally it is possible to modify the author base. It is recommended to make use of this plugin to change it, but it also works with other plugins that have the functionality to customize the author base.

Change Author Link Structure

To prevent that usernames are publically visible, the username in the author's permalink is replaced with the author's ID.

Permalink Editor vs Change Author Link Structure