Russell -- thanks. I deleted all Acrobat preferences, but that didn't seem to fix the problem I had. Perhaps I'm not asking the right question:
Some files with light text and dark background, e.g., http://dnr.louisiana.gov/sec/execdiv/techasmt/presentations/IETC_Chemical_Marketing_Assoc_Inc_20040501.pdf, display properly (light text, dark background) in Safari and Acrobat Reader. But when I open the file in Acrobat Pro, it displays as dark text, dark background.
Other files, e.g., http://www.acer.edu.au/documents/RC2006_Masters_OpeningSlides.pdf, display properly in Safari and Reader. But when I open this file in Acrobat Pro, it displays as dark text, white background.
Which Acrobat Pro setting controls this behavior?
In my earlier search for color changing capabilities, I had selected Digital Printing in Advanced > Preflight and "Executed" and thought that might have permanently changed a setting. Does that make sense?
Thanks for the Output > Composite Gray suggestion; I hadn't seen that.