The sentence here uses "equity" in contrast to "debt." Equity is an ownership interest, in which the equity holder is entitled to a share of the value of the company; it carries a lot of risk but can have a lot of potential upside. Debt is a loan interest, where the debt holder is entitled only to repayment of the debt plus interest (less risk, but no big upside). "Equity papers" would be documents that evidence an equity investment in a company (e.g., stock certificates). "Debt papers" would be something like bonds or other documents that show a debt interest.

"equity" has many meanings. "equity papers" is not a standard collocation so we need context. You may mean the UK actors' trade union "Equity". If you have "Equity papers", you are a member of this union.

"This risk premium is essential in order to induce investors to allocate their capital into equities; otherwise, no one would buy equity paper assets like stocks."