As a tec noob myself I also had no idea PDF's could do this until today and thinking back over the last year how many pdfs have I opened?? I think I also need to wipe my PC not because of this download but because I might have already been effected.
Use Foxit reader instead of Adobe. They are more security conscious and have disabled the javascript functionality by default for a long time. Pretty much everything from Adobe has had lots of security issues. Why browsers have flash enabled by default for so long is beyond me.