Blueprism Interact Forms only supports the upload of one file per field. This will function most of the time if the user is required to only attach one or two files.
However, if many supporting documents are required to be uploaded, current workaround is to request user to perform an extra step of archiving the files. As such, it will be good to have forms to be able to upload multiple files at one time, as what other form based solution can do.