dspdfviewer software package provides Dual-Screen PDF Viewer for LaTeX-beamer, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install dspdfviewer
dspdfviewer is installed in your system.
Make ensure the dspdfviewer package were installed using the commands given below,
$ sudo dpkg-query -l | grep dspdfviewer *
You will get with dspdfviewer package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Text Processing |
| Package | dspdfviewer |
| Version | 1.15-2 |
| Description | Dual-Screen PDF Viewer for LaTeX-beamer |
| Sub Section | Text |