I sometimes use Awesome Screenshot Plus to print a web page. It comes in handy as not all web pages are optimized for printing. This can result in a very long image if the content is multiple pages long, which is also not great for printint it out, since everything will come out as a single page due to scaling (on OSX).
There are probably other ways to solve this, but I've found ImageMagick to work very well in these cases. You'll need to know how many pages you need. For that, you'll need to know the dimensions of the source image. You can also gather this info with ImageMagick.
$ convert doc.jpg -print "Size: %wx%h\n" /dev/null
Now that you know the pixel width and height, use some math to figure out how many pages you'll need. The following is an example for letter size pages (8.5 x 11 inches):
h/((11/8.5)*w)
Round up the number and that's the number of pages you'll need. Now we can use ImageMagick to create a paged pdf from the image:
convert doc.png -crop 1xnumber_of_pages_here@ +repage doc.pdf
Open up doc.pdf to check it.
I'll probably script this up one of these days.