In Acrobat go to Tools > Pages > Extract and chose the pages to Extract as an independant file. If you have Acrobat XI you can export those pages into the Powerpoint and edit it from there. However, if you are trying to copy and paste just text, you want to run OCR first; Tools > Recgonize Text > In this File and then you will be able to copy the text from the PDF and than paste it in the Powerpoint file. That is of course, if it hasn't already been done.
As for copying images, you want to go to Tools > Content > Edit object (Acrobat X) and select the image and right click and copy the picture into the Powerpoint.