Rewordify is an AMAZING site that will simplify difficult text. You can paste text from another source, paste a URL to simplify a website or Rewordify your own documents. No account is needed to use the basic features but if you would like to be able to Rewordify your own documents or share your Rewordified texts you will need to create a free account.

Here are links to the tutorials that I think will be most helpful to you when learning how to use Rewordify.
First Time User Guide
Site Overview Video