E.g. you'd think to search for *.pdf if you want to find a PDF in Firefox history, but this brings up nothing. So what's the correct syntax?
I think you are searching for *.pdf - ie try .pdf!
I discovered the Places database that can be queried with industrial SQLite Manager. For instance, I have got all my PDF files with SQ
SELECT * FROM moz_places where url like '%.pdf'
3 years ago
2 years ago