Hey Cristián,
thanks for your quick reply!
When the user tries to load a page he doesn’t have access to, he’ll be redirected to the Membership Options page, where you can have the message you want. Dashboard -› s2Member® -› General Options -› Membership Options Page
That’s exactly what I want to avoid. Maybe I didn’t articulated my desire right. To make it clearer here are two screenshots of my website: one like a “normal”, not logged-in visitor sees it. The second image is the menu like a logged-in user sees it. As I marked in the second picture, the pages “Mein Konto” and “Chartbibliothek” are only visible to premium users. A “normal” visitor won’t be redirected to another page if he clicks on one of of those since they [the ‘premium sites’] aren’t displayed to them at all.

At the moment, users have to create a WP-account (i.e. as a ‘subscriber’ or ‘contributor’) and I controll the site-capabilites with the Plugin “CaPa Protect”. I am looking for a way to control the user rights directly through the membership levels and not through an additional WP-account from every user.
Regarding my invoice request, if I get you right the only possibility is to upload the invoices as a normal .pdf, then I have to restrict the access to this file so that only the corresponding user has access to it?
My idea was that every user has a “My account” section where he/she can edit the profile information (like adress, passwort, e-mail). This “my account” section should have a site called “My invoices” where all of his/her invoices are stored. I thought it might be possible to browse through the members list and upload some PDF to a certain account, so that these documents automatically appear in the “My Invoices” section of this specific user. This it not possible?
Regards