Search your "Fonts" folder for "Symbol." The internal PostScript name used by software like Adobe Acrobat is often what shows up as SymbolMT .
Summation symbols, square roots, and infinity signs. symbolmtnormal font free
Because it is one of the "Base 14" fonts, many PDF readers can display it even if it isn't "installed" on your specific machine. Why You Might Need It Search your "Fonts" folder for "Symbol