You can save as a high quality jpg then use acrobat pro to convert it to pdf. You'll have to use some form of conversion as far as I know there is no way to save it directly as a pdf.
I prefer to save it as an image file whether be it in jpeg or a better option for zooming functions. And print it from there to be placed as a pdf file. Though there will be more less options you can do from there, once you have decided to publish it portably already. I recommend choosing to save it in raw still just so you will have a back up in case something wrong shoots up.
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You'll have to use some form of conversion as far as I know there is no way to save it directly as a pdf.
There are several free pdf printers available on the net, I use CutePDF.