If you’re running Debian, it is recommended to use the version included in your
distribution. Depending on which Debian release you have, installing dspdfviewer is
a little bit different.
dspdfviewer is included in the distribution since stretch.
You don’t need to activate anything special, simply call
apt-get install dspdfviewer
(or use your favorite GUI to install the dspdfviewer package)
and you’re ready to go.
To see which versions are available in Debian, please take a look at the package tracker.