diff --git a/common/desktop.nix b/common/desktop.nix
index 9f36efd..e4c3486 100644
--- a/common/desktop.nix
+++ b/common/desktop.nix
@@ -31,8 +31,15 @@ in
   services.gnome.gnome-keyring.enable = true;
   security.pam.services.sddm.enableGnomeKeyring = true;
 
-  # Common
+  # Set the PDF viewers to open PDFs.
+  xdg.mime.defaultApplications = {
+    "application/pdf" = [
+      "sioyek.desktop"
+      "zathura.desktop"
+    ];
+  };
 
+  # Common packages.
   environment.systemPackages = with pkgs; [
     awww               # Wayland desktop background daemon with animations
     bemenu             # Program launcher