Identify the symptom

  • Tofu boxes: the font is missing — install or substitute it;
  • Whole-paragraph garbage: wrong encoding — reopen with GBK, UTF-8 or Big5;
  • A few odd glyphs: rare characters missing — switch to common ones or install a large font.

Fixes

  1. Use the Font substitution dialog to map missing fonts to available ones;
  2. Embed fonts before saving important files (File → Options → Save);
  3. Export to PDF so fonts travel with the document.

Prevention

Agree on a standard font list and bake styles into templates to minimise cross-device drift.