Vacuum preservation may be more troublesome for you! It's hard to find anyone to do this in the market. Give you a suggestion: first, see if your certificate is dry. Be sure to dry it! Put it in a plastic bag, and put some desiccant in it to prevent moisture and insects. I believe it's easy to find. Pay attention to the storage environment that must be protected from light to prevent the paper from changing color after being irradiated by light. If the above conditions can be met, then I think it should be no problem to save for 30 years. I hope I can help you. I am a student of library management. If you have any questions, you can trust me privately or keep asking.