Extending WiFi over 3 floors

I've got WiFi in a fifth floor unit of a commercial building. We've recently took on a new unit on the second floor and are wondering if it would be possible to extend the WiFi from the fifth floor all the way down to the second.

The unit on the second floor isn't too far away from the unit on the fifth in that it's just 1 unit beside, 3 floors down.

Would a WiFi extender/repeater work? We do not have access to power points outside our unit.

Thanks in advance!

Edit: if I'm lucky, I am sometimes able to have 1 bar of wifi reception when I'm on the second floor unit

Edit 2: both units are small (approx. 190 sqft)