You could use a check box form field, but that would require protecting the
document for forms, which would prevent other editing in the document unless
you included other form fields. If you'll settle for a form with check boxes
that can be double-clicked, see
http://gregmaxey.mvps.org/Add_Toggle_Objects.htm

If you need a dynamic (clickable) checkbox, there are a number of ways to
create and use clickable checkboxes in documents / templates. Some require
protected or locked forms, others do not. Take a look at the Checkbox
template available at
http://www.addbalance.com/word/download.htm#CheckboxAddIn

for an exploration of these. Some utilize code, others do not.