Adding to what Lori said —
Put the Portfolios under a common parent directory/folder.
Use Acrobat to create a Catalog index of these.
Any PDFs in the Portfolios will have been indexed.
You can have the PDX created 'auto-mount' when a placeholder PDF is opened (Document Properties > Advanced tab). With this PDF opened you engage advanced search and query.
Or, open Acrobat/Reader. Open Search. Browse to and select the PDX. Begin query.