Change WordPress user roles and capabilities › Forums › How to or FAQ › Assign Different Pages to Different custom post type option › Reply To: Assign Different Pages to Different custom post type option
So, you wish to allow paid user to view some page by its ID.
Use Content View Restrictions add-on.
Open page 1 for edit and allow view this page only to the role 1.
Allow view page 2 only to the role 2.
The important step is: assign to a user needed role after payment. You can do it manually with delay to access to a service, or automatically – you need to find appropriate action, executed after payment was finished.