I really like PDF995. It's free or you can register it. I have never done that. The only thing I deal with is a little pop up after every time you print with it. I have been very happy with it. It doesn't add any watermarks like some converters do and it has worked on a large array of paper sizes I use like engineering drawings.
try CutePDF... if you google it, it should come up.
The process after downloading involves just printing, and then when the print dialogue box opens, you select the CutePDF "printer", then you hit "Print" and it sends that file as a pdf to the directory that you selected.