(Courtesy of http://pkp.sfu.ca/support/forum/viewtopic.php?f=8&t=8039&p=31228#p31228, and replicated as described below)

This only seems to happen in Firefox. Each time I click the "Fullscreen" or "Fullscreen Off" buttons while viewing a PDF, the article_galley.view count is incremented by one. As Ute points out, this shouldn't be happening, as this is essentially just a view change, not a whole new article view. 

WRT the above problem: there must be a difference in how the PDF is called between FF and non-FF browsers. In templates/article/article.tpl, there's a good chunk of Javascript that calls the PDF in different ways given different environments, but I'm not particularly familiar with Javascript, and I'm not quite sure whether the problem is in there, or elsewhere. 

NB: The "Download PDF" option also increments the view count by 1, but I consider this correct behaviour -- this action is essentially creating a new version of the file that will be viewed separately.