Yes, you can sharpen pole pruner blades by hand, using a metal file. First, disconnect the pole saw from the power source (if applicable) and clean the blades with a wire brush to remove debris. Then, secure the blades with a vice, to ensure they don’t move whilst you sharpen them. Place the file between each of the metal teeth (it should fit perfectly in the curve of the blade), and move it repeatedly in one direction until the blades are sharp. Use a file with a guide to make things easier, and make sure to sharpen both sides of the blades.