Citation Reference

I downloaded a PDF and saved to my Library. I right clicked on my PDF filed and clicked to "Create Bibliography from Selected Item." I got an error message saying "The Items you have selected contain no references. Please select one of more references and try again."
Can someone tell me how am I to generate a citation from a saved PDF?
Thanks

This is an old discussion that has not been active in a long time. Instead of commenting here, you should start a new discussion. If you think the content of this discussion is still relevant, you can link to it from your new discussion.