1. A method for embedding hidden information in a document comprising characters, comprising: determining hidden information to be embedded in each class of a layout transformation respectively; acquiring a code sequence for each class of the layout transformation by coding the hidden information to be embedded in each class of the layout transformation; performing a layout transformation on characters from the document according to the acquired code sequence for each class of the layout transformation respectively; wherein performing the layout transformation on the characters from the document according to the acquired code sequence for each class of the layout transformation respectively comprises: selecting the characters to be subjected to the layout transformation for each class of the layout transformation from the document respectively, length of the characters to be subjected to the layout transformation being larger than or equal to length of the code sequence corresponding to each class of the layout transformation; performing the layout transformation on the selected characters according to the acquired code sequence for each class of the layout transformation in a cyclic application, each value in the code sequence for each class of the layout transformation corresponding to a transformation number of each class of the layout transformation.