DSpace main use case are open access repositories. It supports to restrict access based on ip addresses or groups of authenticated users. It also supports time-based access restrictions better known as embargoes. These restrictions can be applied to an item or to selected files and manage if a user can find and view the metadata of an item and if a file can be downloaded.

You are asking to limit what someone can do with a file they downloaded. This is beyond the access restrictions that DSpace supports. To support those restrictions you would need an entire digital rights management solution. This consists of encrypted files and client software that can decrypt those files but controls how they can be used. While there are proprietary systems offering something like this, it’s always a race between these systems, the encryption and people trying to circumvent those restrictions by breaking the encryption, hacking the client software or other ways.

To answer your question:

1. DSpace cannot do this and I doubt that the DSpace community will ever accept such functionality even, if someone would try to contribute it. Being a DSpace committer myself, I would veto it.
2. While systems for what you’re asking for exist, most if not all of them are proprietary and closed source.
3. While such system exists, you must expect that people will try to break the restrictions and it is likely that earlier or later they will be successful.
4. Please rethink your use case. Why do you want people to read the content of the files but not use them in any other way? How would you handle a scenario where someone reads the contents and types it into a file manually? Isn’t there a way to make the files available without these restrictions?