Copy a pic in PDF

In Adobe Acrobat Pro, Tools->Select & Zoom->Snapshot Tool.
The current cursor is like this: +. Click and drag a rectangle.

Most of time, I will use Faststone Capture to obtain a picture over the screen, but I believe that softwares as big and cool as Adobe Acrobat, AutoCad, Matlab, etc. must have the saving-picture function.
If you spend time to explore a software, you can fully employ it.