If you have unwanted A4 paper that’s only been printed on 1 side, then it tear or cut it up into halves or quarters. You then end up with A5 or A6 sized notepaper. I’ve got several wads of these around the home, and they’re clipped together using bulldog clips or staples.  Clearly, if you’ve got confidential material on the paper, it’s probably best to shred or burn it instead! You also might want to avoid printing too much in the first place!