Sorry penguin, we're still working our way through all the Forum posts and emails.
To answer your question, the Adobe PDF viewer does not yet support the new garbage collection system in Mac OS X which the Pedias use now. You can either check the preference to "Open links in external browser" in the Preferences/General to open your PDFs in Adobe Reader or if you'd like to continue viewing your PDFs inside Bookpedia delete the plug-in to force Bookpedia to use the default viewer plug-in. You will find the plug-in in your HD under /Library/Inter Plug-ins/AdobePDFViewer.plugin
Or check if there's a newer version of the PDF Viewer to install that supports Garbage collection.
We sent a request to Apple that it should default to the regular PDF viewer when it can't load the Adobe one.