How can I improve the scan quality of the text written with a pencil?

I use a FUJITSU IX500 Scansnap Document Scanner. How can I improve the scan quality of the text written with a pencil?

Example:

Before scanning:

After scanning:

The notes written with a pencil in the header and the footer have a poor quality in the scan.

The issue is that the default scanning mode was auto-color detection:

The auto-color detection must have incorrectly thought that the document was black and white.

Changing it to "gray" fixed this issue:

Note that one shouldn't select "reduce bleed-through", as it would also triggers the issue:

"Increase text contrast" also triggers the issue, so better left unchecked:

Increasing DPI doesn't seem to help improve the scan quality of the text written with a pencil. E.g., at 150 DPI:

vs. at 300 DPI:

However, increasing DPI does help to improve the scan quality of the printed text. E.g., at 150 DPI:

vs. at 300 DPI:

In summary, the following settings seem optimal to scan printed documents containing some text written with a pencil (e.g., course notes with annotations):