Previously when I would use Wordpress, I'd add a plug-in called Yoast. It was fantastic. It would scrub your content to see where you can make improvements.
Fast forward a few years later and now most of my clients are on Magento. There are lots of paid SEO plug-ins you can find on Magento Connect. However, Creare has popped up a few times and its suppose to be free. I've never used it myself but I'll check them out.
But if you're not looking for a plug-in, then SEO Review Tools is worth trying. It gives you everything you need and it's FREE. It has a built in keyword planner and content editor. Two things that will satisfy my SEO friends.
By using a SEO tool doesn't mean that I will change the way in how I write. If anything, it helps with making you more concise.