Hello,
The PC editions are outlined
here. In short, the Logbook Pro Standard Edition licenses you to use one computer for one pilot logbook. The Professional Edition allows you to install Logbook Pro on two computers and activate both computers with one license for the use of one pilot logbook. The Professional Edition adds additional functionality such as PC-to-PC synchronization, FAR 121 features, and FAR 135 features.
A license can be purchased instantly by
clicking here.