Starting Preview without opening previous PostScript documents

I'm running the latest version of OS X and Preview is hanging whenever I try to start it. It attempts to open the documents which I previously had open, which is ~10 PDFs and ~3 PostScript files, and it seems to be permanently get stuck whilst "converting" those PostScript files (even though opening them was no issue before). Hence my question is, how do I start Preview without opening those documents? (I'm guessing there's some kind of cache I should delete.)