If you both use Autodesk Design Review 2008 as well as the keyboard a lot notice that to zoom in and out you need to press CTRL and the + or - key. Combine that with panning using the arrows and you need to press and release the CTRL button. Not so good, but there was hopefully a valid reason for removing the ability to only use the plus or minus key.
Some other useful keyboard shortcuts are:
|Fit to Window (show extents)||F|
|2D Navigation Wheel||Spacebar|
Most commands have keyboard shortcuts. Hover the mouse over a button and as you can see just use E for Distance Measure.
Knowledge Base document: Zooming in and out by pressing +/- keys