How do I sort .pdf files by custom metal data field values?

I have a folder of .pdf files with custom metadata values added to each.  I want to sort files by metadata values.  I think I built and selected the .pdx index file correctly.   I used advanced search, left "What word or phrase would you like to search by?" blank, selected the name of the custom field under "additional cirteria, "Contains" and the field value I want to sort by.  Returns zero results every time.