IS IT POSSIBLE TO BUILD A 12X15 DOUGLAS PERGOLA ON MY EXISTING CONCRETE SLAB WITHOUT CUTTING A FOOTING?

Pergola design.cheapestforyou.com have a look there at products available that come with all the stuff you need as for sitting on concrete that would depend on the depth of your concrete anything less than 4 inches-no-you could cut out a square of concrete for each corner and dig down to a depth of 9 inches from top of your slab put in a concret base and bring some concrete blockwork up to the level of your slab and use those to secure your timber uprights.