There's two approaches. One is try to figure out what the maximum you can charge is and still get a decent number of appointments. Of course you don't get to listen in on all the other phone calls to other notaries in your area, so that's hard.
The other is to figure out how much you need to make it worth your while. You should be considering how much is fair for you to earn per hour. Not the time facing the signer, but the total time to get ready for, perform, and follow up on the appointment. Then add expenses, such as car, paper, toner, and some savings to replace hardware when it wears out.
Electronic document that you print are the default these days, but if you want to separate it out, probably the biggest part that you should be charging for is your time in getting your hands on the document and getting it to print. Maybe 4 out of 5 times that only takes 15 minutes or less, but then there will be ones that they give you the wrong password, or it prints very slow, or for other reasons you spend one or two hours getting the documents printed. So you might want to consider printing to take 30 minutes on average.
If they want scan's sent back, you may want a portable scanner, and you would want to charge enough to recover the cost of that over a reasonable number of appointments. Also, if they want to look at the docs and see if they're satisfied before you can drop the docs at FedEx/UPS, you may find your self hanging around the shipping point for hours; you should charge for the wasted time.