Hi Will,
I just opened an incognito window in Chrome to test this behavior. I filled out one form, and that activity was captured. I then went to another form, and was served up the Download button for the second form. I clicked the button, accessed the content.
I then went into the Marketo lead database and looked up the test lead, and the second form activity didn't record a "Fills out Form" activity for that download. and the trigger which increases lead score for every form fillout didn't increase my lead score.
Should I fill out a support ticket?