I'm currently taking the "Introduction to Data Science" course via Coursera (probably a subject itself for another post as it's been pretty interesting so far even though it's only been going for just over two weeks).
The lecture slides are provided as PDFs, but I like to annotate them with my own notes too. I had been using Print Screen and then just cropping the copied image. But, since I already had ImageMagick installed, I thought I should try automatically converting the PDF slides to individual images.
A command like:
convert -density 300 input.pdf outputname_%0d.png
works pretty well to convert to PNGs.