While Inkscape is an awesome way to do it, for those lacking X11, you can also extract individual pages of a PDF into SVG format using the poppler-utils at the command line. For example, to extract just page 30:
$ pdftocairo -f 30 -l 30 -svg somehugemanual.pdf myextractedpage.svg
You can then use your favorite vector editor (mine is Inkscape) to isolate the image from the text.
Alternately, if you're a hardcore command-line user, you can extract to EPS (encapsulated postscript) and use
sed to hide all the text (which happens to be between BT and ET lines for pdftocairo). Here's how:
$ pdftocairo -f 30 -l 30 -eps manual.pdf - | sed '/BT/,/ET/ d' > myimage.eps
And, if you're really insane to avoid using X11, you can even shrink the bounding box of the image from the command line using Ghostscript's
$ epstoeps myimage.eps myimage-bb.eps
I've tested this and it works great. However, personally, I find it easier to just use Inkscape.