Every time you update a drawing, Tekla Structures creates a new drawing ( .dg ) file in the drawings sub-folder of the model. After that, the previous drawing file is not used.
You can delete the unnecessary drawing files in multi-user mode. Use the advanced option XS_DELETE_UNNECESSARY_DG_FILES to have the unnecessary drawing files deleted automatically when the last user exits the model and saves the model.
By default all unnecessary drawing files are deleted automatically after seven days. Use the advanced option XS_DELETE_UNNECESSARY_DG_FILES_SAFETY_PERIOD to define the time frame after which unnecessary drawing files are deleted.