All methods marked in the help file as "viewer-style" methods cannot be undone. They are intended for fast document generation, not for editing operations.
Use InsertPicture instead of AddPictureEx.
rv.Clear;
<calls to AddNL, AddPictureEx and so on>
rv.Format;
These methods cannot be undone.
Insert* methods insert in the caret position, they are designed to implement editing operations (the only exception is InsertRVFFromStream, its undoable alternative is InsertRVFFromStreamEd)