For this purpose, humans have created numerous rewriting tools to save time and use all words available in the English dictionary. Rewriting tools use millions of synonyms made available to them through artificial intelligence and instructions given by the human mind. If you hire the services of a content writer to rewrite/create content for you, they will charge you a lot. Big organizations can afford this but small startups and students can never afford the services of professional writers.
Think of it this way: What do you have more chance of hitting, a distant, tiny target or the broad side of a barn? For the sake of search engine optimization, you want your website to be the broad side of barn. The more quality articles, or unique readable content, your website or blog offers to search engines (and therefore the general public) the more exposure your website will receive from major search engines.
WordAI also comes with several settings that can help you do the things you need to do. These help make your content more readable and unique so that there will be no issues with Google. One of the things you will surely appreciate about this tool is that this take and replaces words with exactly the same meaning then puts these in the sentences in a way that makes sense to the readers.
Google is getting VERY good at catching spun content so you'd better be talented at manual spins. If they DO catch you, of course they'll spank you... and hard. So anything you use spun content on is inherently AT RISK. Worse yet... Google gets better at finding spun/poor content every year. So in the longrun you're screwed. I'd weight your other options and see if you couldn't find a cheaper source for manually hand written content.
There are some 'free' article spinners out there that require you to enter your text with properly formatted 'spintax' in order to create the end result. But how you need a totally separate tool to create this machine formatted text, so how is this really useful to you? Spinbot does all thinking for you, from taking in the context of every phrase to creating additional textual content that is as readable and meaningful as the text you originally entered.