I am probably missing something really obvious - but every time I export my InDesign document to a PDF, it is showing up as a solid white document.
You mean, 'paper' color, i.e. empty pages? In InDesign, what you see in Preview mode? (hit W being not in Text mode). If everything 'disappears', check your layers options - are they set to 'Print'? Select objects and check Attributes panel - aren't they set to 'Nonprinting'?
Thank you! Something so basic but was driving me insane. Of course - when you start panicking it all gets worse!