Here is my transcript of the PM conversation James and I had about this issue, which we have yet to resolve. However, we'll try the proposed solution and update if it helps.
I can almost certainly confirm that this is a file-size issue. The problem is that it takes a very long time to load a 17+MB PDF file in the browser. Depending on the browser and/or browser PDF plugin, even if the PDF should display incrementally it may not -- it may only display once the entire PDF has been downloaded locally. This would result in you initially seeing only a white screen, but eventually (say on returning to the page) seeing the PDF. (The file will have been partially downloaded previously, and so will probably show up with a bit more waiting; or Firefox etc. may continue to download it in the background even when you leave the page.)
The best solution for your readers would probably be to split the article into multiple PDFs, and upload each individual PDF as a galley for that article, so that you have multiple galley files, each weighing in at a reasonable size. You can modify the galley label (either during the galley upload process or by clicking the "Edit" link next to the galley name in the layout listing) to something that makes more sense for your readers. For example, you can change it from "PDF" to "Part 1 (PDF)", etc. You can also upload the full PDF as well, and for example modify the label to say something like "Full article (17MB PDF)".
Thanks for your quick response! I wonder why this would be an issue only in Firefox and not in other browsers? I was able to load the full-size PDF just fine in IE, Opera and Chrome...
That's a good question; the only answer I can put forward is that different browsers (and probably more specifically, different browser PDF viewer plugins) handle PDFs differently. The file actually caused Firefox on my macbook to crash, although when I brought the page back up I could see the PDF just fine. My suspicion is that there's probably something specific to Firefox that causes problems regardless of the viewer (eg. Adobe Acrobat in Windows; Preview on OS X; etc.).