It's a PDF download link. I tried it a few minutes ago and it still works using Firefox on MacOS (displays better with Preview than with Adobe Reader; QuickTime Player gives a good display if your screen is big enough, but a weird interface with no index).

The main thing I would want an e-reader for is as a tunebook/music stand. The Kindle seems to be a total failure in that department if it can't even download a PDF given a URL for it, let alone display it usefully.