Cant you do that yourself?
This question is completely irrelevant to the problem.
The steam on mac version of the application seemingly cannot write any files, nor can it read any add-ons.
The workaround involves taking the launcher, running it, grabbing the files, and replacing your steam files with them.
On a windows computer, you will have a full keyboard with the page up and down buttons and the number pad.
On mac, you don't have the number pad or the page up or down regardless wether it's a macbook or an actual computer.
This is a real pain because you have to bind all the keys that are binded onto the number pad or the page up and down buttons to something else on the keyboard and it gets messy because I can't remember what some of the stuff I've binded.
For example I had to bind every key that was binded to the the numberpad to a letter instead.
The buttons your keyboard has doesn't have anything to do with the operating system.
You can plug any USB keyboard into a computer or laptop and experience it's full array of keys. Some of these may or may not feature a numpad.