Can't download PDFs (was making PDF available)

Howdy,

I want to make a PDF available from one of my blog pages, but no matter how I fiddle with the tag, I get:

Warning: include(/home/glabagro/public_html/ridesanddives.com/wp-content/themes/sporting_motorcycle/nex_gen.php) [function.include]: failed to open stream: No such file or directory in /home/glabagro/public_html/ridesanddives.com/wp-content/themes/sporting_motorcycle/404.php on line 13

Warning: include() [function.include]: Failed opening ‘/home/glabagro/public_html/ridesanddives.com/wp-content/themes/sporting_motorcycle/nex_gen.php’ for inclusion (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/glabagro/public_html/ridesanddives.com/wp-content/themes/sporting_motorcycle/404.php on line 13

This blog sits on my Host Gator account with several other websites (some functioning, most not) so the directory tree is a little cumbersome. However, where should I store PDFs that I want folks to be able to download? Is there something special I have to do to make WordPress honor the download?

The website is https://www.ridesanddives.com.

Thanks,

Greg