Is there a free PDF editor for macs?

[Niko]

I would like a PDF editor that allows me to edit PDF documents that would be otherwise read only. I have seen some like SmithMicro which sells their PDF editor for like $70. Are they all this expensive is there a cheaper/free alternative?

[Chappers]

Usually you can copy and paste text from a PDF into 'TextEdit' (but not pictures).

This doesn't seem to keep the formating but gives a free way to edit the text.