procedure ClearSelection;
Drops any active selection, resets the anchor / cursor endpoints, and invalidates the viewer so the next paint draws a clean page. Fires OnSelectionChange exactly once when the previous selection was non-empty; idempotent when there is nothing to clear (no event, no invalidation).
Called automatically by the viewer on every state change that would invalidate the selection: SetPdf, SetPageNumber, SetActive(False), and DisplayMode transitions.
PdfView1.ClearSelection;