Okular Document Viewer KDE can be Installed on Ubuntu Linux 21.04 easily in Terminal with Snapcraft Snap & Snapd. Sudo Snap Install command is Used to Install Okular on Ubuntu. Ubuntu has preinstalled Snap & Snapd in it. Just Use Sudo Su command & check the Snap --Version command to verify Snap Installation on your Ubuntu Linux. Snap List command can be used to verify the installed Snaps on your Linux Distro. Okular is a universal document viewer developed by KDE. Okular works on multiple platforms, including but not limited to Linux, Windows, Mac OS X, BSD, etc. Features: Supported Formats: PDF, PS, Tiff, CHM, Djvu, Images, DVI, XPS, ODT, Fiction Book, Comic Book, Plucker, EPub, Fax. Okular also Support Sidebar with contents, thumbnails, reviews and bookmarks. It also features Annotations.