Well, I'm not a PDF expert too. PDF keywords are just ... keywords. Like HTML keywords, you can insert some metatag inside a PDF to list some words related to the PDF content. Keywords are not displayed when you read the PDF with clients like Acrobat Reader, but they're still there to be managed by other clients which will need additional informations which can't be displayed in the document.
I myself found that iText allow you to set keywords in a PDF document (but only prior to write the PDF document itself), while JasperReport can't manage keywords at this moment (if the informations I've gathered are correct, this feature will be implemented in the future). Unfortunately, JasperReport is our main engine to export PDF documents, so I need to find a way to handle keywords via JasperReport somehow or, if this is not possible, to find some other libraries that allow me to add keywords to an existing document.
I still hope my search capabilities are not perfect and I've missed some topic concerning JR and keywords or some other about
Java library which handle PDF documents.
I wonder why PDF has become a standard when it comes to
exchange documents when it is so far from being manageable.