@Kian21 - I'm terribly sorry for the slow response. I wasn't receiving SDN notifications and somehow missed this and your private PM. I don't think it is absolutely necessary to do the keyword highlighting on physical paper, but I do think the tactile experience of it (picking up the marker, moving your hand, etc) does reinforce the whole process and engage you more with the reviewing process. I'd recommend you try both and see if you notice a difference!