I suggest to implement the following feature:
An option is LlSetOptionString or LlExportOptions or LlXSetParameter or something similar that changes the name of the file that is exported from the preview in the Web Viewer.
A typical use case might be:
Someone runs a report in the web viewer as a preview, clicks the export button, and it saves as report.pdf. They expect it so populate with the report name and the date, because they download a lot of reports and don’t want to have to search through report(1).pdf through report(100).pdf.