The proposed sale of Mativ's Engineered Papers business for $620 million could potentially bring in significant revenue for the company, which could strengthen its financial position. However, the impact on the stock price is uncertain as it would depend on how the market perceives this move. If the market views this as a positive step towards focusing on more profitable segments, the stock price could rise. Conversely, if the market perceives this as a sign of trouble in the Engineered Papers business, the stock price could fall.