Understand that the iWork applications are not clones of Word, Excel, or Powerpoint, and do not allow you to directly edit Microsoft documents. When you open them, they are translated into the proprietary Apple document formats, saved in Apple formats, and must be translated again to export to Microsoft document formats. Apple does not guarantee translation, or export accuracy. If you have those Office 2008 fonts backed up somewhere, I would restore them into your home directory : Library : Fonts folder, so they will be available when you need them in Microsoft and Apple documents.
You can purchase the iWork '09 DVD from Amazon or Ebay resellers. For El Capitan (or Sierra) compatibility, you will need to download and install the Apple iWork 9.3 updater. This gets you the latest iWork '09 application updates to Pages '09 v4.3, Numbers '09 v2.3, and Keynote v5.3.
I have the iWork '09 applications running on El Capitan 10.11.6, and all is well, save for some superficial issues (like inability to automatically attach Pages, Word, or PDF files to emails from the Share menu).