Welcome to mobileread Sean
Basically what you have is a file that is restricted by DRM (Digital Rights Management). To put the file on a Kindle you will need to remove the DRM and either convert it to Mobi format (not always pretty with a PDF file) or just move the PDF file over to the Kindle. We can't tell you directly how to remove DRM here on this forum, but it can be done. However, depending on where you live - it might or might not be illegal. I mention that because you say you don't want to do anything illegal. It is up to you decide whether or not you are comfortable with continuing on.
If you are interested in continuing on Google the phrase "Apprentice Alf Blog" and read the entry on being perplexed. You are perplexed - right?
Feel free to come on down to the Kindle forum to hang out. We love new Kindlers.