There are many services on Fiverr that offer proofreading. They talk about all the areas they check in your document.
The truth is that they simply run your document through an automatic grammar check.
I am no different, but I will tell you exactly what you get.
I am going to run through Grammarly, with word choice turned on. This feature means that repetitive words are replaced with synonyms that make sense.
I then run the piece through the Hemingway App. Why? Because while Grammarly provides excellent grammar information, it doesn't help simplify sentences. If the Hemingway app finds a difficult to read sentence, I will correct that.
The end result is not just a grammar check, but a simplicity check.
You want your idea easy to understand, right? Let me do both for you for $5!