Yes, so just documents, email. I'm guessing no social media, or streaming video/music. I would start by using a data estimator (I like this one since it is pretty detailed, just make sure to switch it to "Tablet" even though we're looking at hotspots: http://www.uscellular.com/data/data-estimator.html) If your budget can afford it I would take a look at all of the carriers in your area, and not just Verizon (T-Mobile for instance is $10 less for 5GB than AT&T, Sprint has 1 GB more data for the same price.)

If verizon includes hotspot service with your phone, I would just do that. If they don't it may be more expensive overall to have it added to your phone plan. That all being said, you won't be able to place voice calls at the same time you're using data on your iPad through your iPhone.