Not saying the Poster is unauthorised, but KO toys have all the copyright stuff on them as well... so if this was unauthorised, the person producing it could have put that on there to note who owns the property or to make it look legit.
I didn't have much luck looking for an "aquarius posters" to see if it was legit, as search results kept coming up with horoscope posters and poster companies that do horoscope images.