Question: I'm making a presentation, but I don't want to complicate me learning `beamer`, so I use `article` in `landscape` mode.

How can I use a bigger font in all the document as default size?

24 pt, 36 pt, or any similar size????

```
\documentclass[12pt,a4paper,x11names,landscape]{article}
\usepackage[top=2.5cm, left=3.5cm, bottom=2.5cm, right=2.5cm]{geometry}  % Margenes de la normativa TFG
\usepackage{incgraph,mwe}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[spanish]{babel}
\begin{document}
\incgraph[paper=document][width=\paperwidth,height=\paperheight]{example-image-a.eps}

\Large{jei
dfddd

fd\begin{itemize}
    \item fdfs
    \item fdfdfddd
    \item fdsfs
  \end{itemize}

}
\end{document}

```

Answer: 
Note `\Large{...}` is incorrect, the command does not take an argument, but you want bigger than large anyway:

```
\RequirePackage{fix-cm}
\documentclass[12pt,a4paper,x11names,landscape]{article}
\usepackage[top=2.5cm, left=3.5cm, bottom=2.5cm, right=2.5cm]{geometry}  % Margenes de la normativa TFG
\usepackage{incgraph,mwe}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[spanish]{babel}
\begin{document}
\fontsize{2in}{2.5in}\selectfont
%\incgraph[paper=document][width=\paperwidth,height=\paperheight]{example-image-a.eps}

jei
dfddd

fd\begin{itemize}
    \item fdfs
    \item fdfdfddd
    \item fdsfs
  \end{itemize}

\end{document}

```
Under the default settings for [`beamer`](http://ctan.org/pkg/beamer), it's not the font sizes that are increased, but actually the paper size that is shrunk. Since the output is view in PDF and made-to-fit within the viewer/screen, it appears that the font sizes are very large.

An aspect ratio of 4:3 (resulting in a landscape-style view) is loaded by default using the following settings in [`beamer.cls`](http://mirrors.ctan.org/macros/latex/contrib/beamer/base/beamer.cls):

```
\usepackage[%
  papersize={12.8cm,9.6cm},
  hmargin=1cm,%
  vmargin=0cm,%
  head=0.5cm,% might be changed later
  headsep=0pt,%
  foot=0.5cm% might be changed later
  ]{geometry}

```

Here's a take on your MWE with adjustments similar to the above:

![enter image description here](https://i.stack.imgur.com/NglDt.png)

```
\documentclass[12pt,x11names]{article}
%\usepackage[top=2.5cm, left=3.5cm, bottom=2.5cm, right=2.5cm]{geometry}  % Margenes de la normativa TFG

\usepackage[%
  papersize={12.8cm,9.6cm},
  hmargin=1cm,%
  vmargin=1cm,%
  head=0.5cm,% might be changed later
  headsep=0pt,%
  foot=0.5cm% might be changed later
  ]{geometry}
\usepackage{incgraph,mwe}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\begin{document}

\incgraph[paper=document][width=\paperwidth,height=\paperheight]{example-image}

jei
dfddd

fd

\begin{itemize}
  \item fdfs
  \item fdfdfddd
  \item fdsfs
\end{itemize}

\end{document}

```