Thanks for your suggestions. I ended up using PyPDF2 for splitting out just the cover (first) page, and Wand (ImageMagick wrapper) for converting to PNG. Works quite nicely, and easy to install, given that they can be installed as debian packages that in turn pull in all the dependencies.
I hope to be able to release the first version of the package (collective.filemeta) soon.
P.S. Could someone point out what package(s) in Plone produce the nice formatted (and sometimes even i18n'd) strings for file sizes, ie. "File size 12.4 MB" or similar?