I found out that statistics of PDFs that are clicked are recorded per this other forum post (http://en.forums.wordpress.com/topic/view-stats-from-my-own-visits-clicks-not-being-recorded?replies=5), and tested and see it under 'Clicks' as 'WordPress.com Media'. However, unlike posts and pages, it is not something that can be tracked over time. As in, I can't click on a little magnifying glass to tell me the stats aggregated since the beginning of time (in my blog's world, that is). Is this something that can be done?
The blog I need help with is alexanderchow.wordpress.com.