copying text is not working

Hi if a highlight text from a pdf and use the copy option or the cmd+c shortcut this is what I get: w?q??????D uFD w????D fFtFD IWWSF p?eq??e??X ??????? ??????? ???????? ??????? ??? ??????????? ????????? ?????????F p????? ??????? h?????????D y????? ????? ??????????D g????????F I thought it was because some permission of the document but if I repeat the process outside mendeley this is the result McGarigal, K., Marks, B.J., 1995. FRAGSTATS: Spatial pattern analysis program for quantifying landscape structure. Forest Science Department, Oregon State University, Corvallis. what can I do thanks in advance