Offsetting duplications is GOOD but you have to know how the function thinks. The (ill-documented) trick is that the offset vector of the Duplicate command depends on whatever distance and direction you last duplicated an object via clicking and dragging (that is, Alt-Drag on a Mac or Ctrl+Drag on Windows). For example, to draw a side view of some stairs, draw the rise and run of one step. Then hold Alt [or Ctrl] and drag-duplicate this first step to be the second step. Now the "Duplicate"