How to screen capture high-quality for printing for 300 DPI? On the Mac I am aware of how to do a screen capture, but it creates a 72 DPI image. We need a much higher quality image because it's for printing on a color laser printer. We need to be able to print this out high-quality so it looks good on a 11 x 17 inch paper. Thanks!
Taken from here.

defaults write com.apple.screencapture type pdf
killall SystemUIServer


Several other choices besides pdf and default png, see link.