If an incorrect paper size is specified in the Scanner Settings, then a black border may be created around scanned images.

Check to make sure that the Scanner Settings match the paper size being scanned. Selecting Automatic Page Size Detection in the Scanner Settings options may also help reduce black borders on images, especially in cases where the paper size being scanned is not uniform and varies from page to page. Note that Page Size Detection is only available on certain scanners. It may also be under a different name such as Detect Page Size, Length Control, or Width Control.