drupal 6 search pdf content
In my opinion the best thing to use for file search is the http://drupal.org/project/apachesolr module along with the http://drupal.org/project/apachesolr_attachments module.
I probably wouldn't do file searching without solr.

You would then turn off the basic drupal search page and just use the solr one.

It will require a bit of extra setup though and you might not be able to do it if you are on shared hosting.

There is an issue for combining the search files and search pages here - http://drupal.org/node/368195

Unfortunately there isn't a proper patch to use but there is some code in there.
You will just have to do a bit of work yourself to get it going.