Best WordPress File Sharing plugin that allows admin and site users to upload, manage and share their private files and folders with restricted access via frontend. User Private Files is a private file sharing plugin with frontend file manager (client portal) that will add a file sharing functionality on your WordPress website. Your site users will be able to login and upload their files and manage the access to those files. A perfect frontend dashboard to upload and share private files.
More Details from here: https://wordpress.org/plugins/user-private-files/
Website: https://userprivatefiles.com/