When "Tools" menu items are grayed out, you should see an information bar with the following message: "Cannot retrieve informations about the document. The document could be an invalid pdf document or password protected." This occurs
when PDFRider cannot retrieve necessary informations from the document. This is due to an invalid pdf or if the pdf is password protected (that is why "Security" menu item is still enabled).
If you are using Windows 7, there are some compatibilty problems between this os and the component responsable to get the information from the document (aka pdftk), as discussed
I have tried on my pc (with Windows 7) and after opening the document twice, it worked fine.
I have no more informations at the moment. Sorry.