1. A method for detecting hidden information embedded in a document comprising characters, wherein, a document for detection is formed by embedding hidden information in an original document by performing layout transformation on characters in the original document according to a predetermined embedding rule, and the method comprises: determining layout transformation for each character in the document for detection compared with the original document; obtaining a code sequence embedded in the document for detection based on the layout transformation of each character in the document for detection and the predetermined embedding rule; decoding the code sequence to get the hidden information embedded in the document for detection.