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What was the add-on utility of French origin ?
If the network print device dialog box for the printer, changed, then is that a dialog box in AutoCAD ? if so, it's not the printer that needs changing in language, it would be your AutoCAD software, I would think.
Except for the consideration, that if no other dialogs for the AutoCAD software have changed their language, it may not be the software program AutoCAD that needs language change as a whole, but just the portions that the 'add-on utility' has affected.
(Was the add-on utility such as to involve printing or printed output's appearance? if so, it is only logical that it would affect the AutoCAD printing dialog and change its language to match its own.)
You could uninstall the add-on utility (though with the reservation, that I don't know what kind/name/anything about it.)
Or if worst comes to worst, you could do a System Restore - if the add-on utility was installed just recently - and then you would find AutoCAD completely in English again too hopefully. But if you get to that point, let me know first, so that I can instruct you how to go about the System Restore procedure so as to be likely to get a good result... and tell me what Windows version is on your PC in that case, also.