Just "cut out" a part? Assuming you've imported the PDF document in particular, just click the Crop Tool, add a cropping border, adjust it as necessary and click the commit checkmark (or press Enter).
The suggestion about the "Crop Tool" is because you are in a forum about Photoshop Elements. So, it was assumed you were using Photoshop Elements with the crop tool on a .pdf
The Snipping Tool is part of your Windows operating system. It will capture a .jpg from anything you can get to display on your screen. That is why I suggested it.
The snipping tool is not part of Photoshop Elements or Adobe Reader.
If you have windows, there is an "Accessory" called the "Snipping Tool". It allows you to make a cutout of anything on your screen and save it as a .jpg. I don't know how good the resolution is, but with a .pdf, it may not matter.
Does this mean I have to copy the document out of Adobe Reader onto a Word page and then use the “snipping tool”? I’ve never seen this tool on the Windows Word page but I’ll keep looking.