I want to be able to generate an index on a document by marking a word/phrase and select "add to index". In this document and other documents I open those words will then be marked and become a link to this document and page. This index could be stored in the Okular document archive. And all documents belonging together will also be stored there. A "back" button/hotkey would also be convenient so I can travel back to where the trip through the documents started. Reason: I have several research projects spanning multiple documents. It would be much simpler when I could just create the index to the main source. Later I can just hop between the documents by clicking the generated links to those indexed positions. Thanks