Peerwith provides the platform for the author / client to connect directly to any expert / service provider. We don't provide the service ourselves, our experts do. That is why Peerwith is unique.
You may ask the expert to provide a certificate, in practice none of them does. Peerwith is planning to introduce a certificate program in the near future, but at this point we don't.
If you would like to add information about an edit job provided by one of our experts, when you submit your article with any journal. Then we advise you to provide a link to the profile page of the expert, which works (in our experience) just as good as a certificate.