Sometimes, previous successful unlocks of any secured web links (Web Viewer URLs) can take up space in your browser cache/cookies that can prevent Users from saving a copy in the cache for offline use. This can occur to the browsers used on a desktop computer - whether it runs on Microsoft or Apple- as well as smart phones, tablets, and their respective browsers.
This manual gives you and your readers detailed instructions on how you can clear your browser cache on different browsers on either a Mac or Microsoft Operating System. This particularly affects and benefits Web Viewer users.
Click here for the manual: http://www.vitrium.com/support/pdfs/how_to_clear_your_browser_cache_for_pc_mac_tablets_and_smartphones.pdf