Bookfunnel has always watermarked files and that's one feature that sold me on using them for ARCs--though I'm not sure how practical the precaution is, honestly. Now they have introduced some new features. You can watermark with visible watermarks. It will show your email address on every chapter, or section, of your novel. Particularly for PDFs, this new feature might be worth it? Another feature is the option of not sending epub files at all. You can just have your readers read the book on Bookfunnel's site and they never download the book this way. Problem with this is that many reviewers want a physical copy with a format they're used to reading. Are any of you planning on using these new features?
I always copyright my ARCs and send slightly altered versions to add protection against plagiarism before a book's release. Now I'm thinking about using these features, particularly the pdf one.