Get the high-res image and use a program that allows various zoom levels. You can see it faintly at a mid-level, and then at high zoom, you can see some of the ridges (that you don’t see elsewhere on the document).
Doesn’t mean it’s real...it could be a photoshopped certificate from someone else, for example, but I think that running that route is just going to lead to disappointment.
If the Obama people say it's there, all they have to do is reimage the certifying marking and signature and place it online for inspection.
If the embossing is light, they could smear pencil lead on it to make it clearer for inspection. And furthermore, where is the official signature?
They are either deceptive or incompetent or both.