WHMCS File upload in product/service

Hello In WHMCS, we create products/services. I need a facility where I can upload from files to that product under that client..such as contract. If a client signs a 24 month contract, I mus tbe able to scan that contract and upload it to the billing service i've created for him. The file can be saved in the database, where i must be able to also delete the file via GUI, or when the service gets deleted. The applicant must preferably have WHMCS experience. Tx