How to convert a multi-page PDF file to PNG files, with one PNG file per page of the PDF document?

Using ImageMagick (you'll need Ghostscript installed as well), the command:

convert -density 300 filename.pdf filename.png

will result in a series of files filename-0.png, filename-1.png, filename-2.png, one for each of the pages of the PDF. You'll want to play around with the density setting to get a resolution you like.

You may need to give the full path to convert.exe on Windows; I've only ever done this on Linux, but it should work for Windows too.

Use Ghostscript

-sOutputFile=filename This is a general option telling Ghostscript what to name the output. It can either be a single filename 'tiger.png' or a template 'figure-%03d.jpg' where the %03d is replaced by the page number.

You may find it convenient to use GhostView, the GUI front end.

You can use PDF-XChange. It can export any pages you want to the expected format. Not only PNGs but many other formats are supported too