Quickest way to create a PNG from a PDF

[hollymcr]

I have some print-quality PDFs that I need to convert to PNGs for display purposes. "identify" reports one of them, for example, as:
test.pdf PDF 13824x2592 13824x2592+0+0 DirectClass 16-bit 102.516mb 3.870u 0:05

Using "convert" to resize this to a PNG takes a long time (around 20s):
convert test.pdf -resize 1024x768 test.png

Does anyone have any hints for speeding this up?

Note that the PDF is quite a small file (13k) comprising vector content, so in theory it could be shrunk to a much smaller size (retaining it's vector nature first) before converting to a PNG, although I'd have no idea how to go about doing that.

[fmw42]

IM is may not be the best way to do that. see http://www.imagemagick.org/Usage/formats/#vector