Ah! Thank you for looking. This explains that.
All the documents for the technical section of the website (documentation scans etc.) , and this means a large number of documents, are all in a /docs folder , and were not entered via WordPress.
This is an heritage from the previous non-Wordpress version of the website, and also a way to make the links to these documents “human-readable”.
I thought that the fact of a document being linked to from a WP page would be sufficient for it to be scanned.
I understand now that this is not the way it is setup.
Maybe it would be nice as an extra feature to be able to add a folder to be scanned? Or maybe it doesn’t make sense.
In the meantime I guess we will have to live without the possibility to search on the contents of these documents, as I don’t think we would change all these links.
All the best,
Nicolas