Apparently I've been living in the dark ages. The One Delisle project team just introduced me to Bluebeam Revu and, frankly, I'm not sure how we were marking up PDF drawings before this. It's faster and more responsive than Adobe Acrobat. Everyone's comments sit nicely in the cloud. And you can even take measurements off of the drawings. It kind of feels like a light and friendlier version of AutoCAD (which I haven't used in over a decade). Marking up drawings is something that I do regularly as part my job. Sometimes I do that with trace paper (I did that for probably every suite at Junction House). But more often it has been with Adobe Acrobat. If you're in the same boat and aren't yet using Bluebeam, I would encourage you to check it out.