To see the last edit to a page, click on the date on the bottom of the page.  You'll get a Unix style "diff" showing you what was added, what was deleted, and what was edited. If a lot changed, the differences will be confusing.  

Some have suggested that you can make the diff less confusing if, instead of adding new content to the existing page, you add the new content to a new page which you then link into the existing page.  Then the diff for the existing page will merely show the link to the new page.

However, making "diff" easy to read is an optimization with far less value than writing clearly.  Therefore, don't create new pages merely to make diff clear.  Only create new pages if it makes the content clearer -- consider the cleaner "diff" to be a welcome side-effect.
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CategoryWiki