All of my Logitech devices have come pre-paired. It's when you want to add additional devices to an existing receiver that you need the software. The idea behind the unifying receiver was to not require multiple dongles of you wanted to mix and match keyboard and mice.
This could, of course, be solved with a pairing button on the receiver, however instead of software. I had to get the IT department at work to install the unifying software on my work machine so I could pair a new mouse and keyboard.
