How to display clear screenshots in PDF when default Acrobat page resolution is 110 ppi?

I want screenshots captured on my 96 ppi screen to display clearly in the PDF. But the Acrobat default page resolution display is configured to 110 ppi, not to the system setting of 96 ppi.

1) Why is the Acrobat default display 110 ppi and not 96 ppi?

2) If all Adobe Acrobat and Reader users open PDFs with the default Acrobat setting, how should screenshots taken on a 96 ppi screen be resized to display clearly?

Thanks