It's odd that there are two replies, with one saying the file looks ok if they save as a PDF, and another saying there are two font in there.
I have tried changing the font of the complete lot to something else, then going back to what was the original font, but it makes no difference - I still see the problem. When I run the Unix "grep" command, which looks for strings of text, I see
drkirkby@hawk:~$ grep FontFamily S-parameters-2.02.nb
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia"]},
FontFamily->"Utopia"]},
FontFamily->"Utopia"]},
FontFamily->"Utopia"]}
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
FontFamily->"Utopia",
drkirkby@hawk:~$
so as far as I can determine from looking at the .nb files, there's only one font in the document.
I think I'll just have to cut the dubious sections about, and save as plain text, then hopefully I can add them back.
Dave