New & Existing PDF Backgrounds are the Color Beige (rather than the default white)

Starting about a month ago, all my desktop PDFs had their backrounds changed to beige. Any new PDFs that I create (from email, web pages, conversions, etc.) are now created with the same beige background, as well. I can manullay change these backgrounds back to white. But how do I stop this from happening in the first place? How do I create new PDFs with just the standard white background?

I have attached a sample file with the biege background.

(Note: my background setting is currently set to the default black color in preferences and I've uninstalled and reinstalled Adobe Acrobat DC on my computer)