For years, my app folder was a cluttered mess of PDF apps. There was a separate app for everything: editing, reading, and viewing, an app for an e-book library; and yet another just so I could read my manga on the weekends.
The industry-standard “pro” tools are often bloated, resource-intensive, and increasingly aggressive about subscription schemes, while the default viewers built into operating systems are frequently too basic to be useful.
But following my journey to change subscription apps with free open-source alternatives, I changed my default PDF viewer to Okular. It’s software that positions itself not only as a reader but also as a universal document viewer. After using it for quite a while, I removed every other viewer app from my system.
OS
Windows, macOS, Linux
Developer
KDE
Okular is a free, open-source, multi-platform universal document viewer developed by KDE. It supports numerous formats—including PDF, EPUB, DjVu, and comics—offering features like annotation, text highlighting, and form filling.
It’s one app for everything
It takes care of many of your PDF needs
It delivers on its promise of being a universal document viewer. Most competitors focus on one format and treat the others as afterthoughts. Okular, however, works on the principle centered on inclusiveness and allows all document types to be viewed.
My usual weekly workflow includes juggling between manuals, e-novels, and loads of image assets. Okular supports standard PDF documents and EPub books seamlessly.
But it goes much further. For graphic novel fans or those archiving graphic stories, it offers native support for comic book formats like CBR and CBZ. It can function as an image browser, handling JPEG, PNG, GIF, TIFF, and WebP files.
Okular even visualizes Markdown documents and supports the DjVU format. This wide-ranging compatibility means I no longer need to mentally switch gears or hunt for different applications depending on the file extension. It creates a unified hub for all content consumption.
The interface works for you
No more locked down features
A PDF tool is useless if it only lets you “view.” A productive world requires interaction — drafting, extracting text, and traversing complex scripts. Okular features an advanced user interface designed to manage documents rather than just display them.
The feature I use frequently in my workflow is the annotation mode. It lets me shift my “viewing” into researching. It is incredibly robust, letting users add inline and pop-up notes, underline text for emphasis, mark essential passages, or write their own text directly onto the page.
Okular also fixes copy-paste issues you encounter in many “locked” PDFs. Its selection mode lets you select and copy almost anything from a document and paste it anywhere. Navigation is just as easy.
The Thumbnails panel helps you browse documents with lots of images, and the Content panel lets you quickly find particular chapters in any supported format.
A software that respects your privacy
No need to worry about your data
Credit: Keval Shukla / MUO
In the times when all apps want to fingerprint your activity, Okular’s ethical stance stands out as a big deal. It’s a free software licensed under the GPLv2+ license. This means it’s open-source, and the code is open for all to inspect. The KDE devs also explicitly state that the Okular completely respects your privacy. Which is a must for any PDF viewer.
On the plus side, Okular also received the Blue Angel eco-label. This certification is awarded for being resource and power-efficient. It is rare to consider the carbon footprint of the apps we use, but Okular proves that good software does not always need to eat up all your RAM and drain chunks of battery just to operate.
What about the limitations?
The consequences that come with OSS
Even with all these benefits, many professionals still prefer a paid subscription of “pro” app over a “free” OSS. Some argue that community-maintained tools like Okular can’t match the stability, polish, or features of paid enterprise solutions.
People often worry that switching to a free tool means giving up reliability, or that the software might be abandoned and stop getting updates or support for important business tasks like contract signing.
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The doubts are right at their own accord, but this is not the case with Okular. It’s far from just another open-source hobby project. Okular app has been under active development for a long time. It delivers regular updates with continuous bug fixes and feature additions.
More importantly, Okular is fully equipped for any modern business environment. It has signature support that allows users not only to view and verify embedded digital signatures but also to sign PDFs. This feature allows you to detect if a document has been modified since it was signed, ensuring the integrity of contracts and legal forms.
It’s the only PDF viewer you’ll need
Okular proves that you can get a great open-source alternative without being bloated or burdened by an expensive subscription. By seamlessly handling everything from standard PDFs and EPubs to comic books and Markdown, it truly earns its title as a universal viewer.
Beyond mere viewing, its advanced annotation capabilities and first-class signature support make it a great enterprise-ready tool. Combined with its privacy promises and Blue Angel eco-label for energy efficiency, Okular is a great app. It is fast, ethical, and versatile—making it the definitive upgrade for your digital workflow.
