@BR: pdfinfo is not really designed to be launched standalone only as part of calibre, which is why you need to install the dlls it requires separately to use it standalone. If you want to read metadata from pdf files with calibre tools use:
and to read the raw XMP metadata from the pdf file use
calibre-debug -c 'from calibre.utils.podofo import get_xmp_metadata; print get_xmp_metadata("file.pdf")'
Though note that XMP metadata is UTF-8 encoded and the windows console cannot handle arbitrary UTF-8 encoded text streams.