I have a process in Forms where a submitter would submit uploaded attachments for review. The reviewer will then review the form as well as the attachments and can request for clarifications from the submitter. When the task goes back to the submitter, I use the same submitted form for corrections. On task re-assignment, I do not want the submitter(initiator) to be able to delete the previously submitted attachment and still have the possibility to upload new versions of the attachment. 

What can I use in order to accomplish this?

Thank you,