One thing I've done is to just copy the first viewport to create the second one.
This will result in 2 viewports for "Floor 1" for example.
Then I draw a line in model space from a known point on Floor 1, to that same reference point on Floor 2 (building corner, corner of elevator shaft... anything that's consistent throughout all floors.
Then I'll go back to paper space, select the Floor 2 viewport, drag one grip until the viewport is large enough that I can see both Floor 1 and Floor 2 in that viewport... and use [-pan] (notice the dash) and pick the first point of that line I drew, then the second point of the line, to pan the exact distance. It will maintain the same zoom factor, while panning a set distance accurate to your plans.
Then simply drag a grip of the big viewport to resize it as necessary.
Hope I explained that clearly enough.