How to set up a dual-screen presentation for Beamer slides

This tip will be helpful for anyone who uses Beamer-made slides (or any PDF slides in fact) with a dual-screen setup, where the slides are projected on a big screen from a laptop in extended display mode. And who cares about their neck.

Credit goes to this guy for the solution.

So you’ve made your beautiful Beamer slides (by the way, did you know that “beamer” means “projector” in German?) You put your slides on the projector screen, but you also want to see them on your laptop. You could mirror the laptop’s screen, but often you’d like to have some stuff on the laptop that you don’t want to share, like notes. So you have to crane your neck all the time to see what’s on the big screen. Not very convenient. Definitely not good for your neck.

If you’ve ever worked with Beamer-made slides, you know the feeling. It hurts even more if you’ve seen how presentations work in PowerPoint or Keynote. The laptop screen shows you the current slide, the next slide, notes, remaining time. Do you have to use PowerPoint to have a smooth presentation experience?

Maybe not. The issue seems to be that Beamer slides are in PDF. And PowerPoint or Keynote, by the way, will not let you open PDFs, I wish they could. For a long time I was hoping for some hidden magic function in Beamer that would elevate the presentation experience to the level of PowerPoint. And there is, sort of, but it doesn’t work the way I thought. You still need extra tools.

Thing is, Beamer is just a LaTeX class. It outputs PDF. The solution therefore must involve some PDF viewer. As it turns out, Skim, which is a beautiful PDF viewer for macOS (totally free and well-maintained) has a feature I never realized was there, even though I’ve been using the app for ages.

Skim has an option to show PDF in the presentation mode: View -> Presentation. I never used it because all it seems to do is make the slides full-screen, which you can do without this special mode. What I didn’t realize is that next to that menu item, there is an item for presentation options: View -> Presentation Options.... And there you can do something interesting. There is a field that lets you select a Synchronized Notes Document. You can select either the Current Page, the Next Page, or a different file. You can see where this is going, right?

If you use just your PDF slides in Skim, then you can select the current slide (or the next one depending on your preference) in the presentation options, put your slides on the projector screen, and start the presentation mode. Now on your laptop screen, you will see a window with the slide you chose. And it’s synchronized with the big screen. Problem solved. Still, not quite like the PowerPoint experience, but a definite improvement.

It gets even more awesome. Remember there was an option to choose a different file in the presentation options menu? This is where that hidden magic function in Beamer comes into play. Turns out, in Beamer, you can add notes to the slides. First, use the following option in the preamble, which defines how your notes will look like.

\setbeameroption{show notes on second screen=right}

There are other options, but let’s go with this one for now. To actually add notes to a slide, use the \note command within your frame, like this:

\begin{frame}
Slides text
\note[item]{Notes text}
\end{frame}

When you compile your PDF, you’ll see your slide and the notes side by side.

Now we can use this file together with that extra option in Skim. First, make sure you have just the slides file, which you can get by switching to the \setbeameroption{hide notes} setting in Beamer. Second, compile the auxiliary file (under a different name) with slides plus notes, which you get by switching to the \setbeameroption{show notes on second screen=right} setting. Now open both files in Skim. Put your slides file on the main screen and keep your aux file with notes on your laptop screen. Make sure you have at least two frames, otherwise the Presentation Options... menu in Skim will not be available. In the presentation options, choose your aux file from Synchronized Notes Document. Start the presentation mode. And there you go. The big screen shows the slides. Your laptop shows the slides and the notes. And the two files are in sync. Magic. It’s still a bit clunky to set up and sometimes you have to tinker a bit. But it works. If instead of slides and notes side by side you want to see just your notes on the laptop screen, use the \setbeameroption{show only notes} option.

By the way, for some time I used a somewhat hackish way of having my slides mirrored on the laptop. It involved Zoom, of all the apps. If you share the projector screen on Zoom, you can then open the layout options in Zoom which show you a little window with what you are sharing. And that actually works. The problem is that in a recent update this window cannot be scaled up and is so tiny you can’t really read anything.