I looked over this file on a SmartEvent server and it holds the list of all the completed PDF and CSV exports of reports, including manual and scheduled jobs. Instead of deleting from the file, you can delete these in SmartConsole - Logs & Monitor, and delete them from the Tasks Archive.
This would only work for your management user (and management domain, if applicable). If you need to delete older records for other SmartConsole admins (and in other domains), then you would need to delete these records from the archive.xml file manually for each of those admins/domains. This is what the SK article is referencing.