Update lear documents to reference new model

Update the document services to use the model extensions and get the PDFs if already available

The issue names document services, model extensions, and PDFs but no files, tests, or entry points. Locate the document-service implementation and the model-extension code first, then trace how PDF availability is represented. Done means the services use the extensions and retrieve an existing PDF when one is available.

Written by the indexing model from the issue text.