What can I put inside my shoes to help with foot pain if I stand 8 hours a day?

Firstly, you could consult with a podiatrist. Secondly, choose comfortable, lightweight, sturdy shoes with sufficient support and cushioning. Finally, and perhaps the most important thing to do if you're on your feet all day is to get custom-made orthotics to insert in your shoes for foot support and to reduce strain on your muscles.

Your foot pain could be as a result of any number of reasons from your choice of footwear, to the prolonged standing, to the hardness of the floor, and your general body conditioning. Shoes with proper cushioning and support as well as custom orthotics will prove helpful. if pain persists, please consult a podiatrist.