Fujitsu scansnap ix500 Operator's Manual page 237

Creating Scanned Images Depending on Intended Use (for Windows Users)
3.
Select [None] in [Multifeed Detection] drop-down list.
ATTENTION
If you scan documents of different widths or lengths in one batch with [Check Length] selected,
documents will be detected as multifeeds and scanning cannot be performed. Note that scanning
Letter and A4 size documents in the same batch does not result in multifeed detection.
4.
Click the [OK] button to close the ScanSnap setup dialog box.
5.
Load documents in the ScanSnap.
1.
Align the edges of the documents.
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