If a booklet is available with a purchased album, this will be mentioned on the album page in the information shown to the side of the album artwork.
The booklet will be downloaded at the same time as the tracks from the album.
If you want to download it:
Go to www.qobuz.com
Click on your name in the top right of the screen
Click on “My profile”
In the “My Music” section, go to the “Download” tab
Click on “Access Download” next to the item in question
Click on “Download my music track by track”
Click on “Download (digital booklet)”
I haven’t found an answer to my question: contact our customer service team.