About Setting the Lineweight Scale for a Layout
You can scale lineweights proportionately in a layout with the plot scale.
Typically, lineweights specify the line width of plotted objects and are plotted
with the line width size regardless of the plot scale. Most often, you use the default
plot scale of 1:1 when plotting a layout. However, if you want to plot an E-size layout
that is scaled to fit on an A-size sheet of paper, for example, you can specify lineweights
to be scaled in proportion to the new plot scale.