To reduce the size of the CUPS logs:
Back up the existing configuration settings:
cp /etc/cups/cupsd.conf /etc/cups/cupsd.conf.`date +%Y%m%d.%H%M%S`
Open the /etc/cups/cupsd.conf configuration file in your favorite editor (i.e. vim, nano, Gnome editor, etc.).
Locate the MaxLogSize setting, and change it to a smaller value. For example, 100 MB:
MaxLogSize 100m
Restart the CUPS print service to apply the changes:
service cups restart