I have completed my PCB design, ready to generate Gerber files.  I had placed all components with reference to fiducials related to a centered X=0 / Y=0 axis and fixed them in place.  I now find that the center point of my PCB layout has shifted along with the values for each of the fixed-location components.  How can I shift the grid back to its original orientation to make the fiducials match those required to match my existing design in another drafting program for the device enclosure?