Lineweight can be set as an object property or controlled when plotted by using a plot style. Lineweight settings in the plot style override the object's lineweight at plot time. When you select the Lineweight field in the Plot Style Table Editor, a sample of the lineweight as well as its numeric value are displayed. The default setting for plot style lineweight is Use Object Lineweight. You can modify an existing lineweight if the one you need is not available.
To view plot style lineweights in a layout, select Display Plot Styles under Plot Style Table in the Page Setup dialog box.
You can edit properties for multiple plot styles while in the Plot Style Table Editor.