Changing the permalink structure of your website is something that should be considered and planned before you do anything.
One common issue for new WordPress webmaster is that they forget to change the default permalink at the launch of their site. After a period of time, they might need to change it for better visualisation and SEO purpose. Then they encounter WordPress permalinks not working 404 on Apache. This post shows how to fix this problem. Continue reading WordPress Permalink issue and .htacess file