Rotate print from WPF DocumentViewer

I've got a WPF dialog containing a DocumentViewer:

<DocumentViewer Document="{Binding LabelPrint}" />

LabelPrint is a FixedDocument in the ViewModel:

public FixedDocument Etiket开发者_C百科tDruck {get;set;}

Now when the user prints the document from the DocumentViewer, I need to rotate the FixedDocument for printing to landscape (sometimes). How can I tell the FixedDocument (or the DocumentViewer) it needs to be printed in landscape?