Moving to Acrobat forum.
I don't know of any setting within Distiller which automatically defines a bleed, it is written within the postscript which Distiller processes.
I have noticed a new Press Quality w Doc Bleed.joboption appearing in my system. (I do not recall creating it; but all my distilled pdf's show the setting. (I create many .joboptions in addition to screwing up my system helping in these forums and do not recall every detail), but an Acrobat update might have created this as well.)
Distiller will use the last set option for subsequent jobs; Open Distiller, choose a setting; all subsequent will use that setting.
To my limited MS Word knowledge, a bleed cannot be defined. I expect the bleed is included in the add-in code. An edit of that or change to the Distiller default should fix your dilemma.
How are you concluding that your documents include a bleed?