Q: Preview opens, but all that is visible is a faint outline of my .pdf document

MacBook Air 2015

OS X Yosemite

10.10.5

I use Preview as my default .pdf viewer. Recently when I try to open a file using the program I can see it open, but the file doesn't display.

I can see a faint border outline of my file as evident by a vertical line running through all the folders on the right side of my desktop, but there is nothing apparent on the screen. I've read about others having graphics or text missing from their files, but mine simply won't appear. Again, the file is open as evident by Preview being brought forward, the fact that I can see a faint translucent border overlapping my desktop folders, and Mission Control shows it open (although it's just a blank square), however I simply can't see anything. It's like the window on a house. It is obscuring nothing, I can't see it, but it's there.

The only updates I've done recently was an iTunes thing, a Remote Desktop thing, and the most recent Security update.

Please let me know if you have any idea how to fix this.

I'm in Afghanistan on the Kandahar Air Force Base so I won't have access to an Apple Store anytime soon.

Thanks so much.