@shannonlynd I have seen PDF files indexed that were not linked. Google treats PDF files like webpages, so they will find them unless told not to. I usually add the PDF folder to the robot.txt file like Disallow: /content/pdf. Of course, the folder isn’t needed if it is secure. For some sites were I know we don’t want any PDF files indexed I add, Disallow: /*.pdf$ to prevent any PDF file not put in the folder from being indexed.