How to add string at a specific position in each line

With

awk '{ printf "%-15s %s\n", $1, $2 }' renamed | sort -V

... I get good output from the file renamed. It looks like:

file1           file1.new

But I want to have the output changed to this:

file1           -->  file1.new

I want to add --> at position 15 in each line. How to do that?