I did a search on Apple store for "adobe acrobat" and I got a suggestions only from companies other than Adobe. E.g. the first suggestion was for "PDF Reader Pro - Lite Edition" which sounds like the Acrobat Reader, but its a different product from a company called "PDF Technologies"
I don't think it is right to offer products from other copanies than the requested one without saying so explicitly.
Thanks for reporting your experience. It may well be that the first result was an ad... Did you happen to notice "Ad" anywhere in that first listing?
Unfortunately, in app stores – like on Google – it's possible for someone else (including a competitor) to buy their way onto the top listing... It's always important to keep an eye out for the "Ad" markings and keep that in mind.