RichTextBox is used. Times New Roman, TimesNewRoman, TimesNewRoman,Bold. So the algorithm (correctly) detects TimesNewRoman, TimesNewRoman,Bold as unknown and tries to replace those. But in reality, it didn't do anything because the text didn't contain characters with one of those two fonts, thus leaving the two unknown fonts in the fonttable.Microsoft Sans Serif (different font sizes) and 2x Times New Roman (different font sizes). I'm a bit lost here. Manually replacing the fonttable doesn't work. What can I do?