Ducati MULTISTRADA 1200S ABS 2015 Workshop Manual page 82

Checking rear brake pad wear and replacing brake pads
Warning
The following procedure applies to both vehicle versions.
Check through the slot between the two calliper halves, and make sure that at least 1 mm of the friction material
on pads is visible.
Important
Change both pads even if just one of them is worn.
Remove the safety split pin (1).
Working on the LH side, push the retaining pin (2) until it comes out completely.