I wanted to alter diagrams in a PDF and figured I'd convert it to a postscript file to do that. What got in my way was the LZWDecode filter in my postscript file. Here's what I did to get around it:

1. use qpdf with the --stream-data=uncompress option
2. use pdftops (not pdf2ps)

On the Mac I use homebrew to install the qpdf and poppler packages respectively.

You can convert pdf and ps files using imagemagick, although don't forget to install gs beforehand. The secret sauce option to get high resolution images out was the -density flag. E.g.:

convert -density 525 some_pdf_or_ps_file page%05d.png

I hope that helps you!