Quote:.......I don't think there's a problem with my PDF viewer as I use Google Chrome for that.
A web browser will generally replace transparency with white.
Quote: I'd just like to see if I can get the Background Color to apply to every Layer of the PDF first before I turn to a Script...
That is the best way, when you eventually move to Gimp 3 then those old scripts/plugins do not work.
Prove the concept to yourself. Make an image with layers and "transparent" holes in the layers. then for any particular layer Layer -> Transparency -> Remove Alpha Channel Try using different background colours. That is what happens for the layers when you export your PDF.