This isn’t a duplicate of this question: I’m trying to set a bigger font size for all elements. I managed to make font size 12 instead of 10, but it’s still too small to be readable.
Werner suggests in the comments to use cm-super font or anysize extension. I can’s see such packages in Ubuntu. How can I install them?
Default document classes only allow certain base font sizes (
10pt,11ptor12pt).40ptis not supported. You need to include packages that supports that font size. Likeanyfontsizeorlmodernorcm-super. Then you would use something like\fontsize{40}{51}\selectfontin your document, rather than supplying40ptas a document class option.For installation of packages, see How to install “vanilla” TeXLive on Debian or Ubuntu? or How do I update my TeX distribution?