Rather than using the Search Input/Search Results modules for searching within your site, you can add a basic search to your site that uses Google as the search engine. The advantage of this type of search is that it can also find content in linked files (such as PDFs).
To use this search, add an HTML module to your page and copy/paste the content in the text area into the SOURCE view of the HTML module. You will then need to adjust the settings of the module and activate (check) the Token Replace option.
NOTE: This code was available on another website and is provided as-is with NO support because I didn't create the script.