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.

I should be asking how not to display the green folders

The green folders are the multi-file documents. They can contain many files of different types and the search results will list the whole document if it includes at least one PDF file.

If these search results do not fit your purposes, I recommend raising this with your M-Files representative so you can discuss your needs in detail and find a solution that works.

Thanks!