Several chunks of text in that PDF start with the printable ASCII characters from ! onwards in order until there is a repetition, e.g. Magneto-acoustic triangul

Several chunks of text in that PDF start with the printable ASCII characters from ! onwards in order until there is a repetition, e.g. Magneto-acoustic triangulation from the headline corresponds to !"#$%&'(")'*+&,)-&.,"$#*/"&,'$ which is >>> list('!"#$%&\'(")\'*+&,)-&.,"$#*/"&,\'$'.encode('ascii')) [33, 34, 35, 36, 37, 38, 39, 40, 34, 41, 39, 42, 43, 38, 44, 41, 45, 38, 46, 44, 34, 36, 35, 42, 47, 34, 38, 44, 39, 36] So I think this is probably a PDF font-encoding issue that might've already affected the author's original upload.