Engineering Designer Robert L. Lawrence sends us a tip on zooming while working in a paper space viewport.

"The absolute best way to prevent messed-up zooms in paper space is to lock the viewport. This way one can zoom in or out even while inside the viewport, and the zoom factor will stay the same. It surprises me how many CAD people do not know about this, since many of the CAD files I receive do not have zoom-locked viewports."
 
Notes from Cadalyst Tip Patrol: I can't tell you how many views I've messed up in paper space viewports because I didn't lock the viewport! It's very simple to do, but easy to forget. Once a viewport is locked, you can pan and zoom all you like without changing the scale factor of the viewport; it allows you to work in the space freely.

There are several ways to do it. When a viewport is activated, a lock icon will appear on the status bar. If the current viewport is locked, the icon will appear locked; if not, then the icon will represent an unlocked lock. Another way to lock the viewport is through the Property Manager palette. Select the viewport, scroll down to the miscellaneous section, then toggle the Display Locked option. This is a great method to use if you want to lock or unlock several viewports at once.