The old “legacy” Finale .mus format was not downwards compatible.

Which means that Finale 2010 (and earlier versions) can not open neither Finale 2011 .mus documents nor documents created in versions after Finale 2011.

Finale 2011 (and earlier versions) can not open Finale 2012 .mus documents nor documents created in later versions.

Finale 2012 was the first version with support for Unicode fonts.

Which means that Finale 2012 .mus documents support Unicode.

Finale 2014 and later versions use the new .musx file format.

The .musx file format is downwards compatible.

Which means that Finale 2014 can open .musx documents created in later versions.

Finale 2014 (and later versions) can export to the “legacy” Finale 2012 .mus file format (which supports Unicode).

But they do not have a similar export to the older (non-Unicode) .mus formats, such as the Finale 2011 .mus format, and the Finale 2010 .mus format.

“…  A colleague converted the file to ".mus" …”

That must be the Finale 2012 .mus file format (which supports Unicode).

In Other Words:

There is no direct export from the .musx format to the Finale 2010 .mus format.

Instead you can try exporting the .musx to MusicXML, and then import the MusicXML into Finale 2010.

Some layout settings may get lost, but at least you do not have to re-create the document in Finale 2010.

Bonjour,

Kyle -- if you really want to keep using Finale, your best course of action is to buy the Dorico crossgrade, which will also give you Finale 27.4. Think of it as a Finale upgrade to your 15-year-old version, with a free copy of Dorico thrown in. 

Finale 27.4 will run on Windows 11, and it will ensure that you can open any Finale document. 

Bonjour Christian,

Avant toute chose, je vous conseille de retirer votre adresse mail de votre message, avant qu'elle ne soit repérée et utilisée par des bots malveillants.

Sur PC, de nombreux utilisateurs ont recours à des applications tierces, comme PdfCreator ou CutePdf.

Hey guys, English please. Just like Finale, I don't want to go to an extra step to find out what the conversation is about! LOL!

From Michel Herr:

First and foremost, I recommend removing your email address from your message before it can be detected and used by malicious bots.

On PC, many users use third-party applications, such as PdfCreator or CutePdf.

Christian, all you have to do is PRINT your files to PDF. Microsoft has in the printer setup a Print to PDF file. Choose that as your printer and you should have the pdf file you are looking for. 

French:

Christian, il te suffit d'IMPRIMER tes fichiers au format PDF. Microsoft a intégré une option d'impression au format PDF dans les paramètres de l'imprimante. Choisis-la comme imprimante et tu devrais obtenir le fichier PDF que tu recherches.

Christian,

For your information, a French speaking forum exists : https://finale-aide.fr/