I love shortcuts. Anything to make my work go faster. Here's a really great one for you. When you need to enlarge your page to work on a specific area, click the Z key, then draw a box around the area you need enlarged. It can be just a tiny spot. It will immediately become HUGE, and you can easily deal with whatever issue you need to. I use this method a lot, on things such as cleaning up lines here and there, checking typing and doing a little retouching.
To get back to your original size, press Ctrl+0.