option when exporting a document to PDF. This ensures that anyone who opens your file sees exactly what you designed, no matter what fonts they have installed.
Some PDF creators use F1–F4 differently. However, in 80% of cases from Windows/macOS/Adobe apps: F1 = sans, F2 = serif, F3 = mono, F4 = symbol/dingbats.
Be cautious. Searching “cidfont f1 f2 f3 f4 gratis” sometimes leads to old FTP dumps or suspicious archives (RAR/ZIP) claiming to contain “Adobe internal fonts.” These are usually: