ioslides presentation pdf output is not correct.

[zengqing1]

Regardless of whether you first export as HTML and then use the browser print option, or directly use chrom_print to output the PDF, there may still be empty space at the bottom and right side of each slide page in ioslides presentation.

[zengqing1]

---
title: "Untitled"
output: ioslides_presentation
knit: pagedown::chrome_print
---

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

## R Markdown

This is an R Markdown presentation. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.

When you click the **Knit** button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document.

## Slide with Bullets

- Bullet 1
- Bullet 2
- Bullet 3

## Slide with R Output

```{r cars, echo = TRUE}
summary(cars)
```

## Slide with Plot

```{r pressure}
plot(pressure)
```

try this.

[cderv]

We have already tried in the past to improve printing for ioslides. See #399 (comment)

This is a matter print CSS customization and sizing probably when you print. Using the default setting won't work.
pagedown::chrome_print() lets you pass options for the devtool protocol, among them sizing.

Probably playing with those could help. Otherwise some paged media rules would need to be added.

You could try with this for example

pagedown::chrome_print("test.Rmd", options = list(printBackground = FALSE))

which is probably equivalent to uncheck the box in Chrome Print menu.

Anyhow, happy to add some print CSS rule is you find some, but over the years we have now the experience that IOSLIDES is not the best slide framework to print to PDF.