If using the Chrome browser and nothing appears to happen when clicking on a "View PDF" link in the Library's Discovery catalog, click on the lock icon to the left of the URL in the address bar while you are in Library Search. Choose "Site settings" then scroll down to "Insecure content" and change it to Allow.
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This changes the site setting in Chrome for the Library's Discovery system only - https://ccl.on.worldcat.org - and allows one to view and download PDF files from insecure HTTP servers.