We do not have a download file for the latest version (4.50.0.11250), but you can try downloading it from the developer's site
Download version 4.20.1.9720 from Software Informer
Scanned by 75 antivirus programs on May 24, 2023.
The file is clean, see the report.
Version: 4.20.1.9720 (x86/x64)
Date update: Nov 10, 2014
File name: pc-nis_viewer_4.20_b972.zip
Size: 123 MB