When comparing Nitro Reader Free vs KDE Okular, the Slant community recommends KDE Okular for most people. In the question“What are the best PDF viewers for Windows?” KDE Okular is ranked 5th while Nitro Reader Free is ranked 10th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Can convert files to PDF
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 Rouge file naming of your files
It seems to hide edited saved versions of your PDF s in a secret location. Later when its all locked down you wont be able to access them with another program!
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.