Can you undergo foot surgery just to reduce the size of your feet?

Yes. This would be considered cosmetic surgery. I would not advise it due to risks.
Possible but... It may be possible but this is considered cosmetic surgery. The american orthopaedic foot and ankle society has a position statement against this type of surgery. You can view it at: www.Aofas.Org.
reduce foot size. There are procedures to do all kinds of things. So , yes this can be done. But , it shouldn't be done. As other doc's said , it is not advisable .
DON'T DO THAT. Don't do that. As the old saying goes; "If it ain't broke, don't fix it." What if you have surgery for this very elective problem, and things don't go as planned? Dr. Latva.
Why do you ask? Forgive me. Radical procedures to keep the feet small used to be used in china to cripple girls / women as a vicious means of abusing and controlling them. With this legacy, who wants it? If you have the obsessive idea that your feet are too big, you need to be evaluated for body dysmorphic disorder -- life's hard enough without such thoughts, and treatment may greatly benefit you.