In the past, the scores were in paper, therefore, storage took up space and search was tedious. Nowadays, with the evolution of technology and computer, it is possible to digitize them if you have the right tool.
PhotoScore software is specially designed to digitize paper scores so as to convert them into MIDI file. It is possible to use PDF or scanned file for MIDI conversion. It can interpret the chord diagrams and the guitar tablature. It has lots of features; just download it to discover its capacity.