The guide explains how to install Okular on Ubuntu 20.04 using APT, Snap, or Flatpak and why the KDE‑styled viewer is a solid choice for PDF and e‑book handling. It walks through updating the package list, installing the `okular` package, launching it from the menu or terminal, and highlights that APT ensures all dependencies are satisfied automatically. Alternative methods with Snap and Flatpak are mentioned, noting their isolation advantages and potential drawbacks such as increased disk usage. Finally, common issues like garbled text, crashes due to library mismatches, and missing annotations are addressed with practical fixes, along with a quick tip for setting Okular as the default PDF viewer in Nautilus.

Install Okular on Ubuntu 20.04 – Quick Guide

If you’ve been hunting around the App Store and still can’t find a solid PDF viewer, Okular is your go‑to. It opens PDFs, e‑Books, and even old PostScript files without breaking your brain. Let’s get it installed in minutes.

Why You Should Switch to Okular

I’ve seen people juggling three different viewers just because they couldn’t find one that handled annotations consistently. Okular keeps everything—comments, highlights, form fields—in a single place. Plus, if you’re already on Ubuntu 20.04 and want something that feels native but still has KDE‑style polish, it fits right in.

Install via APT (the easiest route)

1. Refresh your package list

   sudo apt update

Updating ensures you get the latest version of Okular that's been tested for Ubuntu 20.04’s dependencies.

2. Install the package

   sudo apt install okular

APT pulls in everything it needs automatically—no extra configuration required.

3. Launch it

Either click Applications => Document Viewer => Okular or type okular in a terminal.

> APT guarantees that all library dependencies (like libpoppler) are satisfied, so you won’t hit the dreaded “missing shared libraries” error later on.

Alternative: Snap

If for some reason the DEB version behaves oddly, try the Snap package. It’s sandboxed but still works fine.

sudo snap install okular

> Why use Snap: It keeps Okular isolated from your system libraries, which can help if you’re running a heavily customized environment. The trade‑off is slightly larger disk usage and a bit more memory overhead.

Alternative: Flatpak (if you’re already on KDE)

sudo flatpak install flathub org.kde.okular

After that, launch with:

flatpak run org.kde.okular

> Why Flatpak: It’s handy if you want the absolute latest build of Okular without waiting for an official Ubuntu release. Just make sure you have flatpak and the Flathub repository set up.

Common Pitfalls & Fixes

Symptom	Why it happens	Quick fix
PDF opens but text is garbled	Missing font files after a system upgrade.	Install fonts: sudo apt install xfonts-75dpi or sudo apt install ttf-mscorefonts-installer.
Okular crashes on startup	Incompatible version of libpoppler.	Remove old poppler libs first: sudo apt remove libpoppler*, then reinstall Okular.
Annotations disappear after reopening the file	Using an older PDF that doesn’t support annotations, or editing in a different viewer.	Make sure you’re using the same viewer to edit; otherwise export the PDF with annotations embedded.

> Real‑world note: After the 20.04 release, I saw a handful of users complain that Okular would hang when opening very large PDFs. The fix was simply to update to the latest okular from the main repository; the older version shipped with 19.10 had an unpatched memory leak.

Bonus: Open PDF directly from Nautilus

If you want to keep it quick, right‑click a PDF => Open With => Okular. Then select “Always use this application” and you’re set. No more dragging files into a window every time.

That’s all there is to it—no wizardry, no hidden steps. Enjoy a smoother reading experience on Ubuntu 20.04 with Okular running in the background like a quiet, reliable friend.