If the floor area on each floor is fairly small then one 1130AG per floor would probably be OK. Bear in mind however that you may (depending on the construction of the building) get signal penetration between floors so take care to select non-overlapping channels on the APs.
In any such situation a site survey is highly recommended, you might find that one AP can cover two floors due to signal penetration. Bear in mind though that if you have many wireless clients you will need more APs to cater for them and if that's the case then you'll need to reduce transmit power to avoid excessive overlap.
Bottom line; do a survey.
