Answer
On the relevant Presentation Object within a Permission Set, RMB gives a choice between two grant types: 'Grant,' which gives full access, including view, add, edit, and delete, and 'Grant Query,' which restricts the user to view-only access with no ability to add, edit, or delete. Selecting 'Grant Query' rather than 'Grant' for the specific presentation object backing the target screen restricts that user to read-only access on that specific screen.