How can I level concrete pavement for an above-ground pool?
The best bet may be to build a frame around the area you want your pool.  This can be made from either 4x4 pressure treated timbers or pressure treated landscape ties. These can be attached by drilling and screwing through them into the cedar that is already there or by drilling into the concrete to hold stakes (you can use large galvanized nails) that go through the ties. You need to be concerned mostly with lateral shifting and less with holding them down.

This frame should then be filled with several inches of sand, as suggested by uncle brad. Sand is the standard base for both above ground and even in-ground pools that use vinyl liners. While you can trim or shim the frame to be level, that is not really necessary. The sand can be leveled even if the frame is not. You also could size the frame so that it is just outside the edge of the pool, or you could set it back a bit and use concrete paving blocks to form a margin around the pool for walking.