Probably easiest is to start notepad (in all programs->accessories if its not on your desktop) then file->open and navigate to the
svg.schematic.IGBT_79f3ac2404d60fbb3cdfff45e372df67_2_schematic.svg
file and click open. The xml will come up as text ready to edit. Cntrl-f will bring up a search window and entering px in there and click find next should find all the pxs for you. When you are done click file->save and exit notepad and you should be away.
Peter Van Epp