Here’s a weird one for you. I started with a 120k postscript file generated in Adobe Framemaker 7, all text, no graphics, standard system fonts.
I ran it through Adobe Acrobat Distiller 7.0 (part of CS2 Premier, latest release), and got a 480k PDF file. Then, I opened it in Preview 3.0.1 (part of OS X Tiger 10.4, latest release), which automatically converts to PDF for on-screen viewing. I then saved that… and got a 208k PDF file.
Just to be sure, I opened both PDFs in Windows98 (shocker!), and both viewed and printed identically. So… basically… Apple is 230% more efficient at generating a PDF than Adobe (the company that invented the format)?! What the fuck?