Thinking about the version you have you could try the following?
Firstly open the CAD Drawing, View > Zoom > Window / In / or Out
Alternativley i would suggest you move to a newer version of Trueview.
Im not sure of keystrokes actually working within the Trueview interface, please let me know if you do find any. Bare in mind this is the AutoCAD interface that has been stripped out of alot of functionality.
Duncan