Bernhard Riedl

This plugin is a <a href="https://www.bernhard-riedl.com/2010/08/01/tagpages-tags-functionality-for-pages-in-wordpress-30/" rel="nofollow ugc">follow-up</a> to the post which I wrote <a href="https://www.bernhard-riedl.com/2007/10/06/wordpress-23-tagging-posts-and-pages/" rel="nofollow ugc">a few years ago</a>. – The idea was (and still is) to equip pages with <a href="https://en.support.wordpress.com/posts/tags/" rel="nofollow ugc">tags</a> and include their number in a combined posts and pages <a href="https://codex.wordpress.org/Function_Reference/wp_tag_cloud" rel="nofollow ugc">tag-cloud</a>.
TagPages is fully compatible with <a href="https://codex.wordpress.org/Administration_Over_SSL" rel="nofollow ugc">https/SSL/TLS-sites</a> and WordPress multisite network.
Plugin’s website: <a href="https://www.bernhard-riedl.com/projects/" rel="nofollow ugc">https://www.bernhard-riedl.com/projects/</a>
Author’s website: <a href="https://www.bernhard-riedl.com/" rel="nofollow ugc">https://www.bernhard-riedl.com/</a>

TagPages

dangrossman

The Calais Archive Tagger plugin automatically goes through your archives and tags every post you’ve written. The plugin uses the Open Calais API to perform semantic analysis of your post text and suggest tags. If a post already contains a suggested tag, that tag isn’t added, but other new tags found are. It takes about 5 minutes to tag 200 posts.
This plugin requires PHP 5 and the cURL library (both of which are available on most web hosts).
Also see <a href="https://wordpress.org/extend/plugins/calais-auto-tagger/" rel="ugc">WP Calais Auto Tagger</a> for suggesting tags as you write new posts.

WP Calais Archive Tagger

Goes through your archives and adds tags to your posts based on semantic analysis.

TagPages vs WP Calais Archive Tagger