Great DIY!!! Very clearly explained with useful photos.
^ Brake Fluid Bleeding is to replace old brake fluid with new brake fluid. Porsche recommends this be done every two years (regardless of mileage). Brake fluid is hygroscopic so it absorbs water, and too much water in your brake system can lead to mechanical and safety issues.
Bleeding does not necessarily need to be done when you change your brake pads, but if you already have the wheels off the bleed valve is right there. You can check your brake fluid's health with a $20 tester.