How can I prevent my drawings and paper from yellowing over time?
I posted an answer to a similar question on this Exchange.

"The reason [paper turns] yellow is because the paper is made from wood pulp and not cotton. Wood is made up of lignin and cellulos. The yellowing in the result of lignin, still present in the fibres of your paper, oxidizing when exposed to sunlight and air."

"To save [the] paper I would recommend two things, 1) Neutralize the residual acids and 2) Seal the paper from contact with the air."

Details here:

How to remove the yellowish color from my old drawings?