I want to insert invisible text into an existing PDF file, to make it searchable.
For instance, if the user searches for "hello", the PDF reader should send the user to the page where I embedded that text, even though it is not visible.
What Java library should I use?
I would appreciate links to specific API methods to use.
Gratis, ideally open source.
(For the curious: I want to automatically OCR incoming scanned papers and make them searchable, in an Alfresco repository, while still making only the original image visible, with the sometimes-faulty OCR result present on the same page yet invisible)