Change/Convert Hex color number for whole PDF document?

Hi,

I have a huge document that I've discovered has not only hex color black (00000) but also another color that shows up sometimes (262626).  I'm trying to get all text color uniform throughout the PDF (00000).  I know I can do a text box but that would take way too long for the whole document; and besides, it messes up the formatting of my footnotes for some reason.  But when I do the text box I can manually convert the hex color to 00000.  Surely there's a way to do this for the whole document?  When I try to go to Print Production (preflight/color conversions) I can't seem to be able to do what I'm trying to do (for example if I try to convert all to B/W or sRGB).  Whatever I try, the hex color remains the same.  Please help!