If the PCBs holes don't exist for LEDs on each keys then you cant (easily). You can open it up and check.
If you really wanna get super creative, you'll have to insert the LEDs in each switch and either drill into the PCB (make sure you don't damage any traces, or find another way to fit them in there. You'll then have to wire them manually to the 5V rail or where ever the other LEDs go to. It's definitely would not be a quick mod and would take several hours of labor and research.
A forum community dedicated to overclocking enthusiasts and testing the limits of computing. Come join the discussion about computing, builds, collections, displays, models, styles, scales, specifications, reviews, accessories, classifieds, and more!