Create a checklist
Create an additional kind of list type—a checklist—based on the standard unordered list.
Checklists are common in documentation. That is, a list where there’s a little box to check beside each list item rather than a bullet or a number. Your PDF specification calls for one, but out of the box, the PDF plugin doesn’t create checklists.
Your first clue comes from the sentence "little box … rather than a bullet." You can create a special kind of unordered list that uses a box as the bullet. Remember the exercise where you created a new bullet variable (the em-dash) and assigned it to nested unordered list items? Well, you’re going to do something very similar here.