##  Class files

To adjust the font size for the whole document, you can set a global option in the documentclass - see e.g. {{Overleafpage|page=read/kjbnzqbvqhvr|text=see this example} The default article class is limited to 12pt, but you can go up to 14, 17 or 20 points if you use the extarticle class, e.g.: \documentclass[a4paper,17pt]{extarticle} For details, please see http://www.ctan.org/tex-archive/macros/latex/contrib/extsizes.

To change the size of the font within the text you can use commands such as \large—see this blog post on texblog.org for more details and examples.