How are you trying to save as PDF? Through the Save As function in PPT or through the Publishing function of Presenter?
I go to File > Save as > PDF or XPS > and choose the PDF option but that error message then comes up.
Ok, well it may be an issue with Acrobat.
If you are using Adobe Presenter, then you should be able to select the Presenter tab > Publish > PDF tab. Then your Presenter presentation will output as a single page PDF with your Presenter presentation in it.