A digital document system in which a digital document in a communication network is shared between a plurality of stations, said system comprising: a first station (101A) having a first digital document (DD1) comprising a thumbnail data item (TH1) and an original data item (HR1); a second station (102A) having a second digital document (DD2) comprising a thumbnail data item (TH2); and a center station (100A) comprising: calculating means for calculating signatures of the thumbnail data items (TH1, TH2) of the first and second digital documents (DD1, DD2); comparing means for comparing the calculated signatures of the thumbnail data items (TH1, TH2); and transmitting means for transmitting information for accessing the original data item (HR1) of the first digital document (DD1) to the second station (102A) according to a result of the comparison.