Download new version
Check: https://github.com/mozilla/pdf.js/releases
Extract distribution Zip-archive to Deploys\WebViewer\WebViewer\Content\pdf to replace old version.
Edit content\pdf\web\Viewer.js
...
Check: https://github.com/mozilla/pdf.js/releases
Extract distribution Zip-archive to Deploys\WebViewer\WebViewer\Content\pdf to replace old version.
...