It may be because of required symbol's font is not supported. To solve this please download latest tcpdf and replace it in your instance. (/include/tcpdf). Try it.
Navigate to <yoursugarinstance>/#profile, edit it, and change the Import/Export Character Set. I seem to recall dependent on ISO-8859-1 or UTF-8 would determine whether the character would appear and how it'd appear, but try out a few different options.
