Do not make PDF's bigger than the PPT file
The PDF file reported from PPT should never be bigger than the PPT file itself.
However, I have a number of PPT files that, when exported to PDF, triple in file size. This is not good.
I was told PPT might be trying to create "high quality" images (the PPT file contains lots of images), but I don't see how image quality can be increased beyond what is already there in the PPT source.