I find that large expanses of white on my screen can be hard on the eyes, so I’ve customized the colours of my main applications to yellow or white on black. For example, this is what my Emacs window looks like:
I also have MATLAB (via Preferences – Colors) and Thunderbird (via various customizations) set to a black background.
I recently realized that I can get a black background in my two PDF viewers.
Acrobat Pro or Acrobat Reader (Windows or Mac)
Set preferences via
Edit - Preferences - Accessibility - Replace Document Colors - Use High Contrast Colors
which gives the option for white, yellow or green on black, or you can choose a custom background and foreground color.
Call SumatraPDF with the
-invert-colors option, for example as
SumatraPDF.exe -reuse-instance -invert-colors paper.pdf
This is an excellent PDF viewer for use with LaTeX, as it refreshes the view when the PDF file changes, unlike Acrobat.
Unfortunately, for Skim it only appears to be possible to change the colour of the border, not the background or text.