It's not too difficult - there is no need to break anything!. There are three types of pin in these bracelets. Two are flush with the ends of the links and the third has a domed head.
1. One of each pair of flush pins is intended to be user-removable. It pushes out easily, being held in by two tiny rubber o-rings.
2. The other flush pin is a tight push fit and should not need to be removed in normal adjustment.
3. The domed pins are actually two halves, inserted from each side of the link. They just need a firm grasp with fine pliers, and a strong pull! You might be able to start them with a fine blade. Once one side is free you can push the second half out.