Shift Origin
The Shift Origin 
tool moves the drawing’s
coordinate origin — and optionally rotates its axes — so that coordinates you enter
afterwards are measured from a point and direction of your choice.
Shifting the origin
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Select the Shift Origin tool.
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Click the point you want to use as the new origin, or type its coordinates in the Origin box. Hold Ctrl and click to reset the origin back to its default position (0, 0) with no rotation.
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Click a second point to set the direction of the X axis, or type an angle in the Rotate box.
As you position the origin, Pix previews the new X and Y axes so you can see the orientation before you confirm it.