How to find tagged PDFs I have to organize a lot of PDFs and it's possible to add Tags to PDFs through the preview app (not the filesystem tags like red/blue/green). But how to find them? When I open the Spotlight and try to search for a special keyword/tag given to a PDF there is nothing.
According to this answer on Apple's forums, the syntax to use when searching for keywords in PDF's is like so:

kind:PDF keyword

If the keyword contains spaces use double quotes: kind:pdf "multiword keyword here"

Example of searching a PDF with the keyword 'proposal':

kind:pdf proposal

If Spotlight has indexed the file(s), they should show in the results.