Soften the paper grain of a scanned drawing

Hello,
I'm posting this message because I have a question 🙂
A comic strip artist has scanned some of her boards and sent them to me. The grain of the paper is very visible. She would like me to soften the texture for specific reasons.

Do you have any suggestions? What filters or adjustment layers could I use?

I've attached a screenshot.

Thank you for your help.