You would start by writing some code!!
The start for the inline and floating shapes in the maintext storyrange is shown below. It is now up to you to extend that to the headers.
Code:
Sub ScratchMacro()
'A basic Word macro coded by Greg Maxey
Dim oILS As InlineShape
Dim oShp As Shape
For Each oILS In ActiveDocument.InlineShapes
oILS.ConvertToShape
Next oILS
For Each oShp In ActiveDocument.Shapes
oShp.WrapFormat.Type = wdWrapBehind
Next oShp
lbl_Exit:
Exit Sub
End Sub