Apache Redirects to stop linking from other domains not working

Little bit at my wits end on this. I've tried so many different variations
of the redirect code but still can't get the server to halt serving PDF
files from other domains linking to them.

Here is my latest:
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?ourdomain\.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^https://(www\.)?ourdomain\.com/.*$ [NC]
RewriteRule ^.*\.(bmp|tif|gif|jpg|jpeg|jpe|png|pdf)$
https://www.ourdomain.com [R]

I was really just trying to stop two domains from linking to our pdfs but
that code didn't work either so I figured I'd try all domains. I don't
really care about the graphics, just the pdfs, but I left the code in place
from another example I followed.
If anyone could point me to what stops this from working or show how to
stop just a couple of domains that would be great. All code I find
references image linking but I figured a file is a file. Am I incorrect?

***
Regards,
Joe W Holt
Sr Programmer/Developer
Jack Onofrio Dog Shows, LLC
405.427.8181