I want to change the font size to small for the entire document. I searched the web. But I can not find a reasonable answer (one line). Is it possible to change the font size of a latex document with just one command.? Thank.
I think that
\documentclass[10pt]{article}
where you replace 10with whatever font size you want, or perhaps less likely
10
\begin{document} \small
where you replace with \smallany size command you want, maybe what you are looking for.
\small