Its a broken link. I'll report it.

In the meantime, you can access it here: https://www.diyhcg.com/wp-content/up...Manuscript.pdf

Update:

The link has been fixed, but its no longer a download link. Its a view-it-on-the-page i-frame. I will ask the site owner to add a new download link. Its public domain, so there shouldn't be any legal reasons not to continue to offer it.