The CAD Sheets tab displays sheets created in the authoring tool and includes Markup tools.
CAD Sheet Tab
For a CAD Sheet to display under Packages > Viewer > CAD Sheet, the package name should be contained within the sheet name, allowing for extensions like ' - Sheet'. The 2D sheets must be included in the active publish set specified in Revit.
CAD Sheet Markup
The CAD Sheet tab displays sheets created in the authoring tool. Once in STRATUS, tools can be used to Markup the sheet. Since the CAD Sheet tab is available on the Assemblies > Viewer and the Packages > Viewer, the information is consolidated in the Viewer CAD Sheet Markup article for more information.