Continuous Scroll and zoom (%) keyboard shortcuts

I am having trouble reading an e-book that I purchased. After installing Digital Editions, I've found that I can not hold the down-arrow to scroll multiple lines. Rather, I am redundantly tapping down, down, down, down, down, down, down, down, down, down, down, down, and so on; you get the idea. In Acrobat Standard, as well as Acrobat Reader, I can hold the down arrow but that doesn't seem to work in Digital Editions. What is the key to scroll continuously so as to avoid getting carpal tunnel syndrome on my first of hopefully many e-books?

Also, a somewhat related question, I have an ideal text size on my laptop screen, and to get to that size quickly, I usually will press the Ctrl-+ and Ctrl-minus keyboard shortcuts in Reader. What are the equivalent shortcuts in Editions, so that I can be equally productive in reading e-books as I am reading standard Reader content?

Thank you in advance,
Justin Brown