A common point of confusion is the difference between the generic "Symbol" font and "SymbolMT". The crux is that they are . The "Symbol" font you have on your Windows machine might be one version, while "SymbolMT" is often the specific, commercial PostScript version from Monotype. When working with PDF files or cross-platform applications, it is crucial to ensure the correct font version is used to guarantee characters render properly for your audience.
You opened a technical report or academic paper, and instead of Greek symbols or fractions, you see weird blocks, question marks, or random letters.
Most programs (like Word or Photoshop) need to be restarted to initialize new fonts.