How to Convert PowerPoint to PDF for Free
For converting PowerPoint to PDF for free, the only way I could figure out is to use this tool: CutePDF Writer. CutePDF Writer allows users to create PDFs for anything that you can print.
You will find two links on the left side, one for free download, and one for free converter, you need to download both and install them.
Then go to PowerPoint, open your presentation, choose Print, and then choose CutePDF Writer from the drop down menu.