This is not an online problem. Some pdf files and some pages of some files have a black overlay, and I cannot read the material. I can select all and copy, and it will show the text (only) in Word, and I can print the file without a problem, I just can't see it on the monitor. I've tried "show large images," and I've tried changing the reading order. Nothing works. What should I do?
I have solved my own problem, in case anyone has the same one: I unchecked "use 2D graphics acceleration" in the Page Display. No black overlay now.