@Sebastian: You can add the following CSS in “Appearance => Theme Options => Custom CSS” box.
/* For footer Widget Title */
#supplementary .widget-title { font-size: 20px; }
/* For footer Widget Content */
#supplementary .widget { font-size: 14px; }
Note: When you increase the font size you need to change to all responsive design smart devices.
@media screen and (max-width: 1060px) {
/* Add here css for maximum screen size of 1060px */
}
@media screen and (max-width: 960px) {
/* Add here css for maximum screen size of 960px */
}
@media screen and (max-width: 767px) {
/* Add here css for maximum screen size of 767px */
}
@media screen and (max-width: 480px) {
/* Add here css for maximum screen size of 480px */
}
@media screen and (max-width: 320px) {
/* Add here css for maximum screen size of 320px */
}