It's totally understandable to want to protect intellectual property and prevent it from being distributed without your consent. When you share a file with a client in CoachAccountable, you are giving the client access to that file. If the client can view the file, there isn't a way to prevent that file from being downloaded.
In general, protecting shared files on the web is a challenge. You can take steps to make it more difficult for your content to be plagiarized, however.
For written documents, a PDF is significantly harder to copy and paste than a Word or simple text document.
For video and audio files, instead of uploading directly into CoachAccountable, we recommend you use a third-party platform such as Youtube, Vimeo, or Soundcloud and embed the files in CoachAccountable. Doing so takes advantage of the ability of these third-party platforms to restrict download.
Ultimately, we recommend that you use your Agreements (contracts) to specify exactly the license you give to your clients and other users, as well as any legal recourse if they violate those terms.