Short answer – you can’t split diagrams. There is no API into Sparx to get ‘bits’ of a diagram.
I’m currently waiting for a response from Sparx to see if they can externalise the function they use in the RTF generator, in which case we’ll use that.
In the next release, we will support printing of documents which are defined in EA as being ‘Landscape’ orientation, which you can automatically print on their own Landscape orientation page.
I’ll update this post when I know more from Sparx.