Use the snapshot tool to copy and paste into photoshop
The snapshot tool looks like a camera and you might need to go to the add buttons bit and scroll down a bit to find it
you mean printscreen and use paint
For future reference,
Open Photoshop, go to file, open, browse to the pdf and select it, it will then ask you which page you want, so select whichever page, set the resolution and colour mode required and open.
Treat it is any other scan, could not be easier.
Stu