Please see Pic #2 If you are zoomed in, zoom out and check if the blue line has the width you want it to have in proportions with the paper then hold down the Alt key and drag the blue rectangle with the Selection Tool (V) to duplicate it. Please see Pic #1 With the Selection Tool (V) scale the blue rectangle by dragging the left edge until it snaps together with the side of the paper and says “intersect” do the same for the right side. Give it a blue (#689FC4) fill color and no stroke. Now with the Rectangle Tool drag a thin shape somewhere close to the left edge as in the image. Go to top menu View > Smart Guides or use the shortcut Ctrl+U. To add the horizontal lines and align them exactly to the edge of the paper you have to turn on the Smart Guides.