Hello,
you can add extra fields and even file upload on checkout page by N-Media plugin:
http://www.najeebmedia.com/n-media-woocommerce-personalized-checkout-options-manager/
It has also personalized/customized production option manager plugin:
http://www.najeebmedia.com/n-media-woocommerce-personalized-product-options-manager/
I hope it will help