Images from PDF to presentation: low quality
Preview app on 10.6.8 doesn't let you extract images except by selecting then copying and creating a new file from clipboard.

Another way is using the free unix xpdf tools. They come with a utility called pdfimages. I just used it on a PDF and it perfectly extracted the images from the file.

For example...

pdfimages -f 2 -l 2 -j 27487.pdf testname

It extracted the images starting (-f) and ending (-l) on page 2 and saved as JPG.

xpdf is available from HomeBrew.

HTH