For some reason, Combobox questions are treated as boolean true/false when filling in conditional logic on PDF forms. So you can trigger a “Yes” or “No” response based on a combobox field being set (but why would you?). They appear to work correctly in Word docs (that is, they output the text string chosen or filled in the combobox), just not PDFs. This makes comboboxes largely not usable if you use a lot of PDF forms.