Unroll the puff pastry sheet on a floured work surface. Sprinkle the pastry with 2 tablespoons of the cinnamon and 2 tablespoons of the caster sugar.
Fold one edge to the centre, then fold the other edge to the centre. Sprinkle with a little cinnamon and a little sugar. Fold the edges to the centre again, sprinkle again with cinnamon and sugar, and repeat the folding process one more time, sprinkling each time with cinnamon and sugar.
Wrap in cling film, and chill in the fridge for 1 hour.
Preheat the oven to 200 C / Gas 6. Grease a baking tray or line with baking parchment.
Remove the cling film, and cut the pastry into 1.5cm thick slices. Lay the slices on the prepared baking tray.
Bake in the preheated oven until golden, about 12 minutes. Let cool. The palmiers will keep for several days in a tighly sealed tin.