Loop is a Mac app that turns any file into your own branded link, and follows every open, page and signature. Drop a file on the menu bar and you get a link that shows who opened it and how long they read each page, and lets readers mark it up or sign. Links carry your logo, colours and domain, and your files stay in your own Cloudflare account. It costs $49 once, where Dropbox's Standard plan, the first with your branding, is $190 a year.
Loop does not sync folders across your devices, which is where Dropbox leads. Loop vs Dropbox goes through every difference.