Okular is the KDE document viewer with support for a wide range of formats, different view modes and various viewing and selection tools. Okular can be used to open basically any type of document, from PDFs to mobile formats, text or CHM files.

Okular not only has support for PDF, DjVu, XPS and PostScript files, but it will also open MOBI, EPUB, plain text and even CHM help files.

Except for the main viewing area, Okular has a navigation panel with quick access to page thumbnails, bookmarks, document index and annotations. At the bottom there is the page bar, which allows you to quickly jump to any page in the document, or just go to the next or previous page.

The left panel provides quick access to bookmarks or show the contents of the current document:

Okular allows you to zoom in or out, fit the document to width or height of the viewing area, view documents in continuous or non-continuous modes (in non-continuous pages will be displayed by jumping from one to another, without transiting between them). The four view modes are as follows:

• Single page
• Facing pages
• Facing pages (center first page)
• Overview

The Overview mode will display a table with thumbnail previews for several pages at once, while the facing pages mode will show two pages side by side on the same row:

Available view modes:

In addition, you can also rotate the document view left or right, or keep the original orientation. Okular also supports opening new documents in tabs instead of in a separate instance. To do so, enable the option “Open new files in tabs” in the Configure dialog, under the General tab.

The presentation mode will display the document in fullscreen, fit to width and height, with access to quick buttons for slideshow, next and previous pages, but also a drawing mode, which allows you to select and mark certain portions of text using a pencil tool.

There are some interesting tools that Okular provides, available in the Tools menu or via keyboard shortcuts, from Ctrl+1 up to Ctrl+7. There is a text selection tool, which allows to select text from anywhere in the document, or by using a rectangular box around any area in the document. Text will automatically be pasted in the clipboard. Other tools include a magnifier or a zoom tool. One interesting tool is the Table selection, which allows you to select a rectangular area, and then divide it into rows and columns. Text selected this way will be available for pasting with rows delimited by newlines and columns delimited by two tab characters.

Okular provides text-to-speech integration with Jovie, the KDE text-to-speech system. There are two options to speak the current document in the Tools menu.

Another feature of Okular are annotations, which include various tools for drawing or attaching notes to documents. For example you can create text pop-up notes anywhere in the document, draw lines or polygons, highlight, stamp or underline text:

The appearance, colors, font size or alignment of annotations can be changed in the Configuration dialog.

The Configuration dialog allows you to configure annotation tools, presentation mode behavior, appearance, tabs behavior and performance settings. You can also change the default font on a per-format basis.

Okular can export documents as plain text or using the Okular document archive format.