pleats are very frustrating aren't they! I usually put cake on turntable then lay fondant over the cake and smooth the top a little to get any air bubbles out (from centre to edges) Make sure your fondant isn't too thin, it will be easier to get it pleat free. Now I go round the edges and kind of hook a finger or two under the edge with one hand, pulling out away from the cake sligtly, lightly smoothing down the side of the cake with the other hand, from the top down. Then move along and go round the cake, doing the same thing. You will find its possible to smooth out the pleats in this way, by pulling the fondant out and smoothing down. You will find that you are able to ease any creases or pleats out this way. then trim up the excess round the cake (0r cake board, I usually ice the cake and board all in one go!), then use your cake smoother top first, then sides. HTH and good luck!