Which property do I select in filter if I only wish to display pdfs?

You would use a file-based condition in your view or search filter, something like this:

Thanks. I have follow your above advice but it makes no difference. I have also tried the reverse does not contain .docx 

but the folders appear with the pdfs in them.

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Just to say what else is happening:

The filer also contains this:

This works fine but it contain both docxs and pdfs

The results display document objects, so they include the multi-file documents that contain PDF files. It's not possible to only list the PDF files inside multi-file documents with M-Files search.

The results display document objects, so they include the multi-file documents that contain PDF files. It's not possible to only list the PDF files inside multi-file documents with M-Files search.