When a Mart user that has the 'Viewer' profile on a model or catalog tries to switch to another subject area within a Mart model, they get the below error message:
"You do not have Modify permission on the model"
The reason for this is in older versions of erwin, when switching subject areas, the relationships in the model will be redrawn and is considered a modify operation on the model.
So by design, a person with the Viewer profile will always get this message when they try to change from one subject area to another. The workaround is to respond with "Yes" on the message above to detach it so that they can modify and navigate between subject areas.
NOTE: This is no longer an issue in version 9.8 and above and you are able to navigate between subject areas while having the Viewer profile on the model.