You definitely can't direct-stream it; you can only direct-stream if you're not using any filters, and the watermark involves using a filter.

You could certainly export the vid from Premiere as an .avi using a codec (Huffyuv, Panasonic DV, etc) and then tweak it in VDub and save a DivX (or other) version; I do this all the time for web exports anyway, since the original export is usually much too dark for good online viewing. (I *could* change the levels in Premiere, but my computer's so slow and cranky that giving Premiere too much to do usually means Blue Screen Of Death; VDub's faster and more stable.)