Making background black for full screen view of PDFs

My apologies if my newbie question has an obvious answer which my searching through Help and the forums here has quite incompetently missed!

Anyway … when I read PDFs in full screen mode 2 pages up [on a 17" MBP] the pages don’t quite fill the screen horizontally: for PDFs from some journals there is about an inch of background either side. This background is white, and stays resolutely white even if I set the background for full screen editing to be black. I’d like that background to be black. What to do?

I’d also really like a PDF to be displayed one page up in e.g. the original threepane window, and flip to two pages up in full screen mode, but I expect that is too much to ask for???

The PDF display uses always the background color specified in Preferences > PDF & PS (the settings in Preferences > Editing are only used for text editing). In addition, you can modify the PDF display options via the contextual menu while full screen viewing.