Thank you for your reply, I've test it and it's not the solution.
In fact, the ezbinaryfile seems to be a very particular datatype.
I found this post about it : http://ez.no/community/forum/developer/importing_pdf_files_storing_ezbinaryfile_types_using_php/re_importing_pdf_files_storing_ezbinaryfile__6
So now I'm trying to use the function insertRegularFile, just to change the filepath...