To edit a PDF, simply open it in Word. This works best with PDFs that are mostly text.
Go to File > Open.
Find the PDF, and open it (you might have to select Browse and find the PDF in a folder).
Word tells you that it's going to make a copy of the PDF and convert its contents into a format that Word can display. The original PDF won't be changed at all. Select OK.
Note: The converted document might not have a perfect page-to-page correspondence with the original. For example, lines and pages may break at different locations.