Sticky notes can be deleted using the Comments catalogue which will also remove them from the document.

Alternatively:

  1. Select the Hand tool (Hand tool icon) on the main toolbar
    or theSticky Note (Sticky Note tool icon) on the Commenting toolbar (View->Toolbars->Commenting)
  2. Click on the sticky note icon to select it.
  3. Press Backspace or Delete on the keyboard
    or right-click on the sticky note icon and choose Delete.