Hi LandSurvey,
I'm guessing when you plotted to the PDF, you had the same problem? And I'm guessing all the plotters are different - either different models, different types etc.?
Next, make sure you don't have the "plot upsidedown" option box checked. If you're plotting a named view, check the named view in the AutoCAD editing window to be sure you're not viewing it from underneath (negative z value). Is this happening to all files or just this one. If it's just this one, then make sure you perform an audit on the file, if that doesn't help, start a new drawing, with nothing in it - purge it before you do anything, and then insert the drawing giving you trouble. Sometimes that rectifies things.
You didn't mention if this was plain vanilla AutoCAD or something like LandDesktop, Civil or some other flavor, or what version you're using. If you didn't create the file, you may check for either service packs, the latest object enablers etc.
If the labels are blocks, be sure the block itself isn't inserted with a negative scale factor somewhere, meaning it was mirrored or something else with the block.
You've got a bit of homework to do but good luck and let us know how you solve it or if you solve it, you may help someone else...
HTH
Todd