I think it could be beneficial because it would be easier for those who wish to pay. They would not have to do extra step looking for that opportunity.

I personally do not like (in soft words) when button says one thing and delivers something else. So I think renaming Download into ‘Download options’ were you give choice download ‘ free’, ‘donate’, ‘pay for pro’ etc as you like is acceptable and feels good enough. I do not see why in that case it should reduce number of downloads but every prediction is always a prediction and nothing is better then the real life test.