If you download the PDF directly from Tableau Server does that turn out OK ?
Can you share the code you are using ?
Thanks for getting back on this Ciaran!
Actually I was able to resolve this: By using "Full Size"
As long as the dashboard fits perfectly in "Device Preview" (Device Type:Tablet, Model: Generic (1024x768)) the API is able to print all the dashboards correctly to the PDF.
And to answer your question, I was able to print from server, as long as orientation was "Landscape" and size was "Unspecified"