Sitefinity's document search indexes the contents of uploaded files through ITextExtractor
implementations. Out of the box it ships extractors for exactly five MIME types: PDF, DOCX, HTML,
plain text and RTF. Upload a PowerPoint deck or a spreadsheet and only the title is searchable.
These are drop-in replacements and additions, plus the failure handling you need to survive a real document library. Everything here targets .NET Framework 4.8 and the OpenXML SDK that ships with Sitefinity (2.0.5022.0, the original 2008 release), because that is what is on the box.