PDF files replaced by question mark icon in Dock I have pdf files in the Dock of my MacBook Air, I just left them there and everything was fine, now all of a sudden a large question mark comes up and I can't open them.

Any thoughts?
You can drag broken links out of the dock by click and drag them to the middle of the screen. Then use spotlight to locate the files - on your Mac or on a time machine backup before they went missing.