title: Change font size in RMarkdown PDF
body: <p>How can i change the font size of PDF output in RMarkdown? 
  The font to be changed is not in the chunk.
  Example:</p>
  
  <pre><code>---
  title: "Example"
  author: "Tales Martins"
  output:
     pdf_document:
      toc: TRUE
      number_sections: TRUE
  ---
  \newpage
  
  ```{r, include=FALSE, echo=FALSE}
  library(knitr)
  
  ```
  # Introduction
  This is my introduction
  </code></pre>
  
  <p>How can I change the font size of "This is my introduction"?
  Default font is little in PDF output.</p>
  
  <p>Thanks in advance</p>