[Zope] OT Zope book images -> PDF

In light of all the hubbub about the Zope book, I thought I would try and make my own copy of it in PDF format (just for me, of course). I'm finding that Acrobat doesn't know how to convert the PNG image file type used in the Zope Book. (or rather, I don't know how to get it to work !) Anyone know how to get png files into Acrobat? Oh, I'm trying to use their 'Open Web Page' method of creating the document. Is there another/better way that will get the png images? Thanks, Eric.