In librsvg, we have a request to make it possible for SVG's <a xlink:href="some_url_here"> element to create the corresponding link in PDF output.
I have no experience at all with the actual PDF format, but from what I could understand in the spec, one creates links relative to a rectangular region, not to arbitrary objects. I don't know if this is correct.
Would it be possible to have some API that only goes to the PDF surface, so that one could create links?
cairo_pdf_surface_create_link(surf, x, y, w, h, url) - something like that?
Never mind, this is supported since Cairo 1.15.4.