So your link is http....file.pdf, and it opens OK on FF but not Safari? But, on Safari a similar link from other sites works OK? Odd. There are two places to start looking: 1) that Adobe's PDF viewer (or some equivalent) is properly installed on Safari, and displays other sites with similar links OK, and 2) talk with your host as to how your server is set up to serve such files, and whether you need to add some sort of header or .htaccess setting to properly handle PDF files. Maybe your default server setup is serving PDF files in a slightly "off" manner that FF can still tolerate, but Safari can't? If Safari can open PDF files on other sites, it sounds like the Adobe viewer is working OK, but you never know.