When comparing Calibre vs KDE Okular, the Slant community recommends Calibre for most people. In the question“What are the best desktop readers?” Calibre is ranked 1st while KDE Okular is ranked 3rd. The most important reason people chose Calibre is:
Features include metadata editing and downloading, coverpage downloading., book tagging and categorization, webpage-to-ebook converter for popular websites, etc. Lots of plugins available to extend functionality.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Powerful book management software, very customizable and scriptable
Features include metadata editing and downloading, coverpage downloading., book tagging and categorization, webpage-to-ebook converter for popular websites, etc. Lots of plugins available to extend functionality.
Pro Cross-platform
Calibre is available for Linux, OS X, and Windows, 32-bit or 64-bit.
Pro Open Source
Pro Portable
Calibre has an optional portable build that can be stored on external media along with the users library. It can then be opened from the external media on any windows device.
Pro Free and open source
Pro Trim margins
Easily trim margins either automatically or manually for easier reading
Pro Featureful
Pro Table selection
Pro Tabbed view option
Pro Supports touch interaction
Cons
Con Average, non-power users might find the interface somewhat daunting
The interface, while functional is not the most attractive or intuitive which may put some people off and discourage their use.
Con Can't save text highlights or annotate
Con No XFA Adobe Forms support
Cannot fill PDF Forms created with Adobe.
Con Requires many KDE libraries
Con No middle-mouse auto-scrolling
Instead of scrolling automatically when holding down the mouse wheel and dragging, it instead zooms in or out, in contrast with many other programs.
Con Poor HiDPI support
You may have to tinker with QT__SCALE_FACTOR environment variables to get the desired size and not blurry content (this is a bug; see https://bugs.kde.org/show_bug.cgi?id=362856 and https://bugs.archlinux.org/task/54688)
Con No search results overview
You have to navigate to next/previous hit one by one
Con No "fit to page" option under printing settings
You can only print the content as given so, when you receive a bigger or smaller image thant the default of the printer, you will have to edit it first on other editor.
Con Slow scroll
Its new ultra-slow-scroll for PgUp and PgDn makes it unuseable.