LanguagePreferences.DefaultEditingLanguage

public EditingLanguage DefaultEditingLanguage { get; set; }

LoadOptions loadOptions = new LoadOptions();
// Selecting the default editing language may affect the document layout during rendering.
// This behavior is similar to how changing the default editing language in Microsoft Word can alter the document layout.
loadOptions.LanguagePreferences.DefaultEditingLanguage = EditingLanguage.ChinesePRC;

Converter.Create()
    .From(MyDir+"Simple.docx", loadOptions)
    .To(ArtifactsDir + "LanguagePreferences.DefaultEditingLanguage.pdf")
    .Execute();