The error Duplicate Document Number commonly appears when the Bold QuickBooks Integration fails its attempt at creating a Sales Receipt during export.
This error appears when a sales receipt in the export has already been exported to your QuickBooks accounting software. (IE. a duplicate sales receipt)
All sales receipts must have unique names.
You have a Sales Receipt in QuickBooks Online titled #1001. You then try to export a Shopify order also titled #1001. Because of this, the export will fail, as you cannot have multiple Sales Receipts in QuickBooks Online with the same document number.