SSH User for dumps/backup

Hello,

I want to download the backups per scp on my local pc (ubuntu desktop).

How can i add a seperat user on ssh for the directory "/var/lib/psa/dumps/domains" so that i must not download from root user account?

This new user (ex. backup) just have access to "/var/lib/psa/dumps/domains"?

Maybe only with read permission

Thanks in advance?