Do I have to ask for money for my document?

No, you don’t have to charge for the documents you upload on Stuvia. You are allowed to share your documents for free as well. 

Tip: Combine the sale of free documents with those that are not free. By putting up some free documents on Stuvia, students can download these to see what level of quality you offer. After they’ve downloaded and studied from these documents, they might be willing to purchase your other documents as well next time.