Scribd Plugin Dead and Possible Replacements
I believe that the plugin Scribd iPaper which has allowed for Sribd embeds for a while, but hasn't been updated in many years, finally died with a recent WP upgrade. I think that the fuctionality can be reproduced somewhat by Jetpack, so you might want to alert people using the old plugin to switch.
Another solution is the new (but unrated) plugin Scribd Doc Embedder. I would like to request that it be added to the Commons as it provides extra shortcode customization functionality that Jetpack does not provide.