documentclass[a4paper]{scrartcl}
usepackage{lipsum}
begin{document}
lipsum[1-20]
end{document}

documentclass[a4paper,10pt]{scrartcl}
usepackage{lipsum}
begin{document}
lipsum[1-20]
end{document}

documentclass[10pt,DIV=9]{scrartcl}
usepackage{blindtext}
begin{document}
blindtext[6]
end{document}