In Acrobat's/Reader's do you have the 'Use local fonts only' selected in the "Page Display' category?
If so uncheck that option. It would your local fonts to be used and not the font metrics used by the creator of the PDF. The square boxes indicate a missing glyph.
If that does not fix the issue, then the creator of the PDF did not embed the font metrics, and you need to contact that person about the issue.