Well, it's possible to revise a drawing without revising a model (you could change a note on the drawing that does not affect the 3D data). Also, if the drawing is fully loaded, not opened view only, it will be up to date with the model. My practice is not to have revision levels on the model like drawings.
Must be this is a PDM thing, I feel like I'm missing something, and I don't use PDM.
Revision information is in the Custom Properties of the files. This information is not automatically added unless a PDM system is involved in controlling the revision levels.
Welcome to the forum.
Like Troy said, revisions are best managed in a PDM vault system.
With that said a custom property can be created outside of a PDM system
and manually maintained. With this the properties can be checked in SW explorer
looking under the properties tab.