Yes, that works. But first you have to open an account with a bookshop that sells pocketbooks. I registered with Lüthy, buchhaus.ch, everything works online. If you open the account before you start using the pocketbook, you can register the reader directly with your chosen bookseller. If not, the pocketbook helpdesk will take care of it in a few minutes.
You can then use the account to register for the pocketbook cloud.
I then downloaded my "thalia"/tolino books to pocketbook by logging into "thalia" via my browser. Once the books are on the device, you then upload them to the pocketbook cloud.
This requires patience, as the browser is very sluggish.