For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos/openSUSE_Tumbleweed/home:ecsos.repo
zypper refresh
zypper install pdfsam
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos/15.5/home:ecsos.repo
zypper refresh
zypper install pdfsam
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos/15.4/home:ecsos.repo
zypper refresh
zypper install pdfsam
For 15.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos/15.3/home:ecsos.repo
zypper refresh
zypper install pdfsam