Answered
I have a PDF that someone else created. It contains some mathematical equations that are visible---as far as I can tell---only through the Examine Document--->Show Hidden Text option.
Is there a way to make this hidden text visible in the main document?
If that doesn't work, what clues does it give you, color, position on top of another color etc. I quite often get white text dissapear when clients are supplying PDFX/1a compliant files as often they set white to overprint for some reason resulting in it dissappearing! :-( This can be fixed up in the fix up panel in the preflight panel.
Hope some of it helps.