Edge is a daily cognitive enhancer which will produce effects cumulatively as you take it over a period of several weeks. Boost has a more immediate and noticeable effect due to the caffeine and L-theanine, meaning it's great for smaller windows of time in which you need that extra lift.
You can most certainly take them together as a 'stack' or take them on the same day at different times as you feel necessary. Just remember Edge is taken daily, Boost is as required.
In any case be sure not to exceed the maximum dose per day, per product and use them as part of a healthy, balanced diet and lifestyle.