Foot/Leg Pain

I recently started a new job where I'm on my feet/walking around for around 6 hours a day,3 days a week. I'm 42 and a bit over my ideal weight which I'm aware can put extra stress on legs and feet.
My question is that my feet and knees are hurting now,so what kinds of things can I do to support these things so I can do my job? I alternate different shoes throughout the week and am also looking for ideas for shoe/foot support.