PDF Creator Toolbar Installed Without My Asking It To

I opened Firefox this morning to find the PDFforge Yahoo Toolbar attached to my browser, which I promptly uninstalled.  What's weird is that I haven't upgraded to a new version of the PDFforge; I didn't do anything.  It just appeared.

1.  Why would that happen?

2.  Now that I've unistalled the toolbar is there anything else I have to do to COMPLETELY get rid of it?