PDX is not all that big, and there is only the one main lobby with two (now interconnected) concourses. So if you're meeting inside, the colleague can just be waiting for you after security at the appropriate concourse. If he or she is picking you up outside (lower level) it should not be difficult to find each other. There is a cell phone waiting area. They can sit there, and you can call them when you land, and they can swing arond.