A family of Microsoft word processing software products for creating web, email, and print documents.
Windows 11 still runs very old versions of Office, so buying a new edition was probably not necessary.
Newer versions of Office have different colors in the default Office color theme, so if you had used theme colors in your documents, you could see a change in them.
If text that was formerly bold is not appearing that way now, you most likely had a font installed that has not be installed under your new version of Windows. If you can post what font is showing this effect, I may be able to help you with that.