You might need to provide us with more information to start...
I assume you are trying to open a schematic or wiring diagram for your shop? if you can't download it, contact the party who you are trying to download it from. You will need at least a DWG viewer to see the drawing. many are available for free. you will need a CAD program such as AUTOCAD to make any changes to the drawing.
The more information you give, the better answers you will receive.
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