The present invention relates to a computer-implemented method for the signed registration of a file, preferably a PDF-based document, by a user in a blockchain, said method comprising the steps of: (a) receiving said file from said user; (b) processing said file and calculating a hash for said file, said step (b) comprising the sub-steps (b.i) processing said file by creating and/or revising a file identifier comprised in said file so that it is unique with respect to the blockchain, obtaining a uniquely identified file; (b.ii) calculating the hash of said uniquely identified file comprising said file identifier with a cryptographic hash function; (b.iii) optionally, determining if the hash obtained in step (b.ii) is unique with respect to the blockchain and if so, ending step (b); if not, resuming from step (b.i); (c) establishing a file reference taking into account said hash; and (d) registering said file reference in the blockchain.