Extract Images From a PDF

Reads each page's content for the images drawn on it and saves them at their original resolution — often larger than they appear, since a picture printed small may have been placed at full size. Tiny graphics such as bullets and rules are skipped by default, because they are technically images and never what anyone means.

Why did it find nothing in my scan?

On a scan the whole page is one image, so there is nothing embedded to pull out. Use PDF to Images instead.

What resolution do I get?

Whatever was stored in the document, which is often higher than the printed size suggests.

Why were some graphics skipped?

They were below the size limit. Lower it to include them.