As PDF viewers, we offer Adobe Reader, Evince, Atril document viewer and okular. There is also qpdfview.
Although Adobe Reader is the official viewer for the format, it is not always the best, especially since Linux development is almost non-existent at Adobe these days, and the version is falling behind its Windows and Mac OS counterparts.
The free viewers work best with the desktop environment for which they were made:
okular for KDE,
evince for Gnome, and
atril for Mate and Cinnamon (and probably a good default for other desktops as well). But feel free to use whatever tool you like best.
Many programs have a way to export a document as PDF file. In addition, the standard print dialog has an option to
print to file, which creates PDF or PostScript files.
For TeX and LaTeX, there are separate processors
pdflatex which produce PDF directly (but they require figures to be in PDF format as well), or
dvipdf to convert a DVI file to PDF.
pdftk is no longer working on current versions of Linux. For the moment, it is still available on a few RedHat 6 machines.