I assumed that user is referring to "Viewer" role in Pro (standalone .sp file).
Create a custom role with 3D permission set to only "Read".
Create a user and assign this custom role.
Log in as this user.
Try export 3D (File> Export) and it is possible.
I also tried export to schedule and it is also possible.
Export .sp is not possible.
So the conclusion is that even if users are assigned to roles with permissions set to "Read" for Schedule and 3D, they can still export Schedule/ 3D (and even Excel). But they cannot export .sp (as .sp file contains internal Synchro data that may contain usernames and passwords, etc.)
So "Read" permissions means read/export. and "Write" permissons means read/write/import.
Additionally - if user only wants to View, then OpenViewer should be used as it is positioned as the desktop app to review the .sp file in standalone workflow.
Permssions for roles in 4D Pro are explained as follows:
Read: can read and export
Write: can read/write and import
Therefore in 4D Pro even if user only has roles with permissions for Schedule and 3D set to "Read" only, they can still export 3D and schedule.
However if user is not authoring 4D, they should use SYNCHRO OpenViewer in lieu of SYNCHRO Pro/ 4D Pro. SYNCHRO OpenViewer does not have File> Export.