It would be great, if selecting and copying to clipboard would work. Maybe the same way KPDF does it: Showing a selection rectangle while dragging and then on mouse-release showing a context menu with the options "Copy to clipboard as text" and "Copy to clipboard as image".
Since the behaviour of dragging the mouse should be controllable (does it mean panning, i.e. dragging the document around in the viewing area, or does it mean selecting), it is necessary to have this as a tool bar item. Therefore this issue depends on #2112373 (we first need the cool bar).
For this feature, we need additional API in the pdf-renderer in order to access the text contents (plain text with associated coordinates).
I opened a feature request:
https://pdf-renderer.dev.java.net/issues/show_bug.cgi?id=47