That's currently not possible using just Embed API. However, It would be
easy enough to integrate our PDF Services API to "split" the PDF file
and retrieve only the pages requested and return that to the browser.
Are you asking if only one page of a multi-page PDF can be downloaded to
the local device or if the viewer will byte-serve the PDF a page at a
time and start to show it before the full file is downloaded?
I haven't seen the roadmap but to the best of my knowledge, we're
targeting PDF 2.0 with Embed API and I suspect you know what that
implies. Also, I don't recognize your screen name or I'd have said "Hi"
too.
Dynamic XFA forms are not supported and only the AcroForm fallback is
supported for Static XFA. At this time, no JavaScript or FormCalc is
supported and no field properties are supported.