This is straightforward since we can simply query PDFDocument for a selection representing text for the entire document.
<rdar://problem/122230652>
Pull request: https://github.com/WebKit/WebKit/pull/23809
Committed 274056@main (1a2dfd4eb52b): <https://commits.webkit.org/274056@main> Reviewed commits have been landed. Closing PR #23809 and removing active labels.