I just purchased this pack but can't download it until I get home but was wondering: Can you pause the game while issuing commands to your commandos?

As far as I remember from the first Commandos, it was strictly real-time, so you can not give orders to your troops while paused. I think it is also not possible in the newer versions, but I am not sure about those.

Learn the shortcuts, that will save a lot of time ;)

No, these games are all strictly real-time. However, because of the way they are, it is fully possible to get by without needing to pause, even though that would be cool. It is best to learn the shortcuts and then think out a way to kill or incapacitate your enemies. Sometimes a plan will need to be tried several times, but don't give up hope-- finally pulling off a complex strategy is very rewarding.