What iPad app will allow me to present .PDFs or .PPTs that include OTF (and other) fonts?
It might be that the fonts aren't being embedded into the PDF, that would cause them to not render correctly on a computer that did not have the fonts installed and Adobe Reader may be faking the look of fonts that it doesn't have. Open the PDF in Acrobat on your PC and in the "File" menu select "Properties..." and then click on the "Fonts" tab. Each font listed should have a remark like "Embedded" or "Embedded Subset".

If that is the case, you may have to change your PDF creation settings (not sure how you are creating the PDFs, so I'm no help there) to make sure that all fonts are embedded.