Ruling on buying study notes for which the owner has not given permission for them to be copied and sold
Question

My relative is asking me this question and is waiting for a response.
She has tests and she was making copies of notes belonging to another girl who had notes on a subject that my relative does not have. 
When she asked her permission to copy the notes she had, the other girl apologised and said that the notes did not belong to her. When the girl left, my relative was surprised when the library worker gave her papers that were copies of the other girl’s notes. My relative took them and paid for them, but she does not want to start revising from them until she finds out the ruling. Please note that the notes are in her house right now, and I believe that they are the only source she has for revising this subject and she does not know the girl who owns the original notes.
Praise be to Allah.What the library worker did of copying the notes without the owner’s permission is a transgression and wrongdoing. It is not permissible for one who knows the situation to copy or buy these notes; if he does so, then he is a partner in the transgression and sin. Intellectual property rights -- such as written works and inventions -- are protected and belong to the authors; it is not permissible to transgress against them. For more information, please see the answer to question no. 129191  
Based on that, your relative does not have the right to make use of these notes; rather she should return them to the library and get her money back. And she should advise the library worker and point out her mistake to her. 
If she needs notes on this subject, she should look for them among her friends or in other libraries. 
And Allah knows best.