bunyip:~ bernard$ pdftk Biology_compos_2012.pdf output repaired.pdf verbose
pdftk(371,0x7fff700b4cc0) malloc: *** error for object 0x10418c880: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap
bunyip:~ bernard$ pdftk Biology_compos_2012.pdf verbose
pdftk(379,0x7fff700b4cc0) malloc: *** error for object 0x10418c880: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap
bunyip:~ bernard$ pdftk verbose
Error: Unexpected command-line data: 
      verbose
   where we were expecting an input PDF filename,
   operation (e.g. "cat") or "input_pw".  Exiting.
Errors encountered.  No output created.
Done.  Input errors, so no output created.
pdftk(382,0x7fff700b4cc0) malloc: *** error for object 0x10418c880: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap
bunyip:~ bernard$ pdftk -v
pdftk(471,0x7fff700b4cc0) malloc: *** error for object 0x10418c880: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap
bunyip:~ bernard$ pdftk --version

pdftk 1.44 a Handy Tool for Manipulating PDF Documents
Copyright (C) 2003-10, Sid Steward - Please Visit: www.pdftk.com
This is free software; see the source code for copying conditions. There is
NO warranty, not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
bunyip:~ bernard$