Hi,
I find this to be hard to accomplish. There should be a specific (READ_ONLY) participant role for this but it does not exist.
There is no way to do this 100%. You can add the user in a process supervisor participant, but the link URL will not work for delegated users since you need to add an extra url parameter.
The way I got this to work is with a custom Web API call that uses Web Service calls to WorkflowGen to figure out the URL.
Hopefully, WorkflowGen will come up with a better solution.
By the way this affects not only the form archive, but all FILE data variable that you might have in a process.