If you upload confidential documents/files as attachments to LibGuides: Be sure to password protect confidential attachment files when uploading. If you do not, anyone can in theory open the file if they have the URL for that attachment (look under 'edit' option next to each file to password-protect.. it's the very last option when you scroll down).
Do not give the file a name or description that you wouldn't want anyone else to see - even if others can't open your file, it is still possible that they can see that it exists when they are logged in to LibGuides.
If you want to make your file attachment 100% private (even file's name can't be seen by others at Woodbury who are logged into LibGuides), then you should upload the file to a secure 3rd party service like Dropbox or Google Drive, and then link to it in your password-protected libguide.