Using the F12 console in Chromium... I don't see that there's even a PDF behind that thing. I honestly cannot tell how that flash player document viewer thing is generating or retrieving its content.
If you click the ORANGE button on that download page, the one with the star-in-circle icon, you may be able to get in through there. Clicking it brings up a dialog box for a login. In there, there's a set of four tiny icons. Second-in-from-right tiny icon is a Github logo. Click that and, if you've a Github account, you can probably get through. I have one such account, but (as is often the case with me) I've long since forgotten my login credentials entirely... so, good luck.
There also appears to be a pay-us-money option... the "VIP" GREEN button below the other three.