Fujitsu ScanSnap N1800 Operator's Manual page 296

The stacker holds the document sheets after they have been scanned. It can
be pulled out and adjusted to the size of the document being scanned.
4. Load the documents into the ADF paper chute.
Load the document front side down, with the top of the document entering the
scanner first (when multiple document sheets are loaded, the last page is on the
top).
If [Face-up] is selected on the [Paper Face Direction] window, load the
document front side up, with the bottom of the document entering the scanner
first.
For details about how to load the document, refer to
Direction" (page 366).
296
6.1 Loading Documents
"6.9.6 Document Feed