A document is an asset type over which an entity can grant a security interest under Article 9 of the UCC.
UCC §7-201(2) states where goods including distilled spirits and agricultural commodities are stored under a statute requiring a bond against withdrawal or a license for the issuance of receipts in the name of warehouse receipts, a receipt issued for the goods has like effect as a warehouse receipt even though issued by a person who is the owner of the goods and is not a warehouseman.