Autocad layout Page Setup manager
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Open the file ACA5-01.dwg in folder 7074 . Will lineweights be scaled in plots from the A1 layout tab of this drawing?
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Each layout tab is set up, usually when created, to fit a suitable plotter. To check the properties of an existing layout tab right mouse key over the tab and access Page setup manager. See if there is a tick in the scale lineweights box.
In this case check that you are looking at the pagesetup manager for the A1 layout tab.