At the center of GoodReader's many features is an excellent PDF reader/annotation app.
To draw a vertical line.
Open the PDF. When you are working on the PDF will ask you if you want to make a new copy for annotations, or use the current one. Do whatever works best for you.
Tap in the center of the screen so that the menus appear. At right will be your annotation tools. Tap the straight line tool, about two thirds of the way down. This will open a Line tool at the top right. Select the color and other attributes you want.
Tap somewhere near where you want the line. Drag the end points on the line until it is where you want it. There is a subtle snapping action to the vertical and horizontal angles. When the line is where you want it, tap Done in the popup menu that follows it around.
If you need to change it, you can edit all the characteristics of the line by tapping on it and working through the popup menu.