How to extract bookmarks from a PDF file

Here is a working solution. However you will need to adjust it to fit your needs.

In my example i removed the first page of a PDF, and then i needed to update the bookmarks to point to the correct locations.

1. remove page 1 from in.pdf:

   pdftk A=in.pdf cat A2-end output temp.pdf
   

2. create a in.info file from in.pdf:

   pdftk in.pdf dump_data > in.info
   

3. in.info needs to be corrected in my case, since i will remove a page.

   Thus, i need to decrease BookmarkPageNumber by one for the bookmarks to lead to the correct pages.

   php code:

   $file = "in.info";
   $data = file_get_contents($file);
   
   foreach (explode("\n", $data) as $row) {
       $tmp = explode(": ", $row);
   
       if ($tmp[0] == "BookmarkPageNumber") {
           if ($tmp[1] != "1") $tmp[1]--;
           echo $tmp[0].": ".$tmp[1]."\n";
       } else {
           echo $row."\n";
       }
   }
   

4. create final out.pdf:

   pdftk temp.pdf update_info in2.info output out.pdf
   

tested working on debian using pdftk 2.01

It looks to me like from version 1.45 (2012-12-06), pdftk does allow modification of bookmarks via the update_info command:

You can now add or change a PDF’s bookmarks using update_info.

via: http://www.pdflabs.com/docs/pdftk-version-history/