Graphical notes can be deleted using the Comments catalogue which will also remove them from the document.
- Select the Hand tool () on the main toolbar
or the Stamp tool () on the Commenting toolbar (View->Toolbars->Commenting)
- Right-click on the stamp and choose Properties...
Change the Appearance of the stamp as well as it’s Opacity - handy if you want the page's contents to show through. The Appearance drop-down menu will only show built-in stamps (user defined stamps are not included)