Prevent indexing of weekly pdf

Not sure where to post this, so apologies if I've added this thread to the wrong location...I have a site with a downloadable pdf newsletter document. The pdf title changes from week to week. How can I stop Google from indexing this pdf?My website is hosted on a apache server so I've used 301 redirects to direct traffic away from expired webpages. I'm hoping to avoid the need to update the htaccess file every week to redirect traffic away from the expired newsletters. Is there a single line of code I can add that basically says, ignore indexing all newsletters from this download point?Any information you can provide would be greatly appreciated. Thanks.

You have to edit your robots.txt, and deny it from there, this stops se from going in there (supposedly) However there should be plenty of decent wp plugins that can help.
The only real way is to not have any public links to it, which again isn't very reliable.

If you have a private login then that would solve it.

if you have those pdfs in one folder on the website in robots.txt put Disallow for this folder i.e