About Linked Models that Require an Upgrade
If you open a model that contains one or more Revit LT links, a message displays if a linked model needs to be upgraded to the current software release.
Audit a Model
Use the Audit function periodically to maintain the health of a Revit model, when preparing to upgrade the software, or as needed to locate and correct issues.
About Revit Viewer
To open and review models without an active license, you can run Revit LT in viewer mode. Revit LT Viewer is intended for reviewing models and printing views and sheets without the need for a software license or subscription.