In the community function lib there is a function to run a microflow as another user (executeMicroflowAsUser). Maybe you can create users with the desired language settings and use these to run the microflow creating the documents in different languages and triggers this by the user that is creating the documents.
Herman, what is the trigger for generating a document in a certain language?
I've did this based on language documents, and document template configurations which where attached to a entity for generating documents based on a language trigger. In my case the trigger was a language set in the ERP system.