How to make a Emission shader RECEIVE shadows? I have baked a floor onto a texture which then I plugged onto an emission shader. However, the floor no longer receives shadows because of it. 

However I have a character walking on the floor and I need the character to cast a shadow on the floor. How do I make the emission shader receive shadows?
You can't, either use a shadowcatcher plane that you composite on top of your footage or don't use Emission shader on a surface that is supposed to receive shadow.