The -add-bookmarks file adds bookmarks as specified by a
bookmarks file, a text file in ASCII or UTF8 encoding and in the same format as that produced by the
-list-bookmarks option. If there are any bookmarks in the input PDF
already, they are discarded. For example, if the file bookmarks.txt
contains the output from -list-bookmarks above, then the command
adds the bookmarks to the input file, writing to out.pdf. An error
will be given if the bookmarks file is not in the correct form (in particular,
the numbers in the first column which specify the level must form a proper
tree with no entry being more than one greater than the last).