How to change language of an existing Pages for iCloud document?

I have document that was created in Pages for Mac with the correct spelling/language (not English) settings for each paragraph. However, when I now try to edit this document using Pages for iCloud the spelling is set to English. I have read several support documents about this Pages for iCloud: Work in other languages Pages for iCloud: Search, replace, and spell-check text iCloud: Change the language or time zone on iCloud.com as well as some "third party" suggestions, all to no avail. I have made sure that the correct language is my primary language in my browser (Chrome), in my OS (Win 10), changed the language of the iCloud UI (through Settings), changed the format used by iCloud (also via Settings) but my document is still spelled in English. I believe the first link above explains how one create a completely new document in a certain language but my document already exists. How do I change the language used for spell-check on an existing document?