Slitherine

And how do I go about doing so if it is? I have previously always bought a physical boxed copy of games if possible, but I want to experiment with buying digital then buying the boxed copy along a bigger order of boxed copies of other games in one shipment, mostly for economy of shipping costs. How would I go about doing so. Note that since I don't think I have bought digital before I am unsure how the procedure works in upgrading.

For the moment the only games who allow upgrading are the following ones:
http://www.matrixgames.com/store/boxedupgrade.asp

Please also note that with those upgrades you won't receive a disc containing the game.

Thank's for the clarification! Seems strange that you only get a box, but thanks for clearing it up. I will just continue with my practice of grabbing my physical copy. I really appreciate that you have this option, I am rather old school and feel the digital download do not give much of a sense of ownership, or something to show friends. I also enjoy swag, and some of the wargame manuals in the physical copies are very well done even though Slitherine/Matrix games don't usually have swag (except for that one war game that had an option for a 7 meter length super size map of the world!!!!). I would be very interested in getting special swag edition games if Slitherine ever decides to go for that.