Opaque and dangerous system
This is a terrifying breach of document security. Your system is so opaque and so complicated that I cannot figure out how to use it correctly. Now it appears that ANYONE with the link can access my private business documents, and there's nothing I can do to secure it or delete these items.
"When sharing a file for Viewing or Reviewing the default behavior allows anyone with the link to access the file either by signing in or entering as a guest."
Yes. This is the problem. When Acrobat invites me to "Add Files" there is no indication that these files will be posted online for anyone with the link to read. Your system needs to say "WARNING: THE FILES YOU POST HERE WILL BE AVAILABLE TO ANYONE WITH THE LINK ONLINE. CONFIRM BEFORE PROCEEDING." You guys assume that I know what your system does. In fact YOU know what it does, I do not.
Admincfrench (Product Manager, Adobe) commented
When sharing a file for Viewing or Reviewing the default behavior allows anyone with the link to access the file either by signing in or entering as a guest.
We also offer enterprise configurations to restrict sharing to selected domains. When those configurations are in place, recipients are also required to sign in and can only access the file if they have been invited. Here's more information on that https://helpx.adobe.com/enterprise/using/sharing-restrictions.html
From your comments, it also sounds like you'd like more options to control who can access files when you share them. We have a few feature requests for that. Please add your vote to those that would be most valuable to you, or feel free to suggest other options.