How to search for PDFs without text?

I heard a podcast the other day where the interviewee said they had made a smart group to find any PDFs in their database without text, so that they could then select them a convert them to PDF+Text.

However I can’t work out how to replicate this! In the column view there are two different “Kinds” – “PDF” and “PDF+Text” – but in a smart group the only option you get for “Kind is” (or is not) is “PDF/PS”.

Does anyone know how you can do this?

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That IS the option to choose.

Yep, but that is only the first half. Consider adding a second option like so:

Ah, many thanks! I couldn’t figure out the second half – that works perfectly.