Of course it must be downloaded in order to display it. Obviously what I mean is that since they point out "auto-download" specifically I would think that they mean that it's saved to disk in your Downloads folder. Why this should be a problem somehow you'll have to ask them not me.

If they file size was the concern, they would have said so. There are a lot of web pages that weigh in at more bytes than this PDF these days with all of their images and scripts and god-knows-what.