pdftk update_info command raising a warning which I don't understand
Solution 1:
using redirection in that fashion
pdftk .\test.pdf dump_data > test.info
will cause this known problem by building wrong file structure, so change to
pdftk .\test.pdf dump_data output test.info
In addition check your alterations are correctly balanced (and no unusual characters) then save the edited output file in the same encoding.
Note:- you may need to consider
Use dump_data_utf8 and update_info_utf8 in order to properly display characters in scripts other than Latin (e. g. oriental CJK)