Full URL of PDF in Google search results

Use this URL to search - http://www.google.com/custom

It will then list the complete URL of the PDF

After downloading the file, go to Downloads (which is accessed via pressing Ctrl+J on Windows and Linux). The URL, which is underneath the filename, may be truncated there, too, but don't worry if it is - just right-click on the URL, and choose Copy Link Address. That will copy the full URL onto your clipboard.