After doing the obvious things like restarting InDesign and restarting the OS (and on Mac, clearing the font caches), the next step I would take would be to save the document as IDML and create a completely fresh copy from the IDML file. That ensures that the problem didn't come from some cruft that built up in the InDesign file itself during editing.
If the problem persists, create a new blank document of one or two pages and fill it with placeholder text using the troublesome font. If the problem appears when you export that to PDF, but not if you use a different, known good font, then the font file is probably corrupt and needs to be repaired or replaced.
If that still doesn't fix it, make sure that the font allows embedding. The font tab in Acrobat's
Preferences > Properties panel will give you the clue to that.
This may be a version-specific problem related to Acrobat, since you don't say which version you are working with. There were a number of printing and text-rendering issues that were fixed in an update to Acrobat and Reader X (I don't know of any for XI). It's always a good idea to check for updates anyway.
As a next-to-last resort, reset InDesign's preferences using Ctl-Alt-Shift/Cmd-Opt-Shift while InDesign is loading.
Let us know the results.