Scale kable table to fit page width

How do you format a table in pdf using kable function? Because my output table width exceeds the width of the pdf. Here is an example:

---
output: pdf_document
---

```{r}
df <- cbind(mtcars[1:5,], mtcars[1:5,])
knitr::kable(df)
```

One option is to use kable_styling from the kableExtra package. The option latex_options="scale_down" will fit the table within the paper margins. See the vignette for detailed examples on all of the formatting options.

---
output: pdf_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE)
library(knitr)
library(kableExtra)
```

```{r}
kable(cbind(mtcars[1:5,], mtcars[1:5,]))
```

```{r}
kable(cbind(mtcars[1:5,], mtcars[1:5,]), format="latex", booktabs=TRUE) %>% 
  kable_styling(latex_options="scale_down")
```