I'm a big fan of plain text and CSV files, as they are probably the formats that will last conceptually forever - unlike the Office formats we use today (including ODS/ODT etc). You may lose the layout information but the "meat" is always preserved.

The PDF to Text converters only work with documents which have been generated from a WP application. Scans of a printed document generally only produce an embedded JPG image.

A few years ago I created a system that employed many of the commands you mention in your episode to convert a document into pure ASCII text, then create a non-repeating list of all the words it contains, along with an instance count (using SQL). By applying this to the contents of a document library the database was used to populate a "search by keyword" system for that library.

Populating the database from several hundred Word and PDF documents took only a couple of minutes. The subsequent keyword searches were very fast and produced a list of relevant documents ranked by the number of instances of the keyword. It was very easy to combine keywords using SQL "AND" and "OR" qualifiers.