There is no trial - the "Try Desktop Docs" button just links you to a stripe payment.
Also it's a bit ambiguous if it searches documents? All the screenshots of are of image search, but the features say you can search inside PDFs and docs, though "All Your Files" says images and videos only-
We aren't offering a trial right now, but to answer about docs --> we're testing an update to support searching text and will be releasing it soon. Right now you can search the contents of all your images and videos.