Great question. Docverter will charge you the smaller of 1) your selected payment plan, 2) your payment plan + the additional per document charge * the number of additional documents, or 3) the next payment plan up. Does that sound fair, or do you think it would be better to get cut off? Maybe a toggle switch in account settings?
The smallest would always be #1. You probably meant to only say 2 and 3. I think a toggle switch would be a good idea. That's how most services allow you to control your spending.
