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It depends on what you mean by "legitimate". They have been on the web since October 2015, and different websites list them as being valid (ex. https://repdigger.com/reviews/first-page-web-listings) but they don't appear to do anything different than a lot of other companies claim they can do.
They aren't listed on a lot of the websites that tracks scams so that's a positive sign.
However, anytime you deal with a company that appears to have been online less than a year there is some risk and if you are looking for ways to "drive" your company onto the first few pages of Google searches then you may want to consider hiring a local company.