How do I change my permalinks for static pages & update existing links?

Hi. How do I change my permalinks for static pages & update existing links?
I have been developing my website using Weaver II with all static pages. There are many internal links, and I am using a table plugin (WP-table reloaded) with lots of links using the default permalink. I was unaware until now that my permalinks are a valuable commodity when it comes to SEO, and I now know that I need to change my existing permalinks so that the keyword of each page shows rather than the existing default page id #, etc. How do I change my existing permalinks so that I do not break all of the links, and then establish the additional pages/links (so that nothing is broken), etc? Is there a plugin to do this? My website is physiciansnutrition.com, so if you need to take a look. Thank you so much!!