The main difference between the .Net Professional Edition (Version 9)  and the Developer Edition (Version 10) is Master Pages and Source Code availability.  These are two major changes, that open up the door for much more customization ability.  There are also dozens of undocumented changes, mostly related to performance and overall feature improvements.  

All PDshop downloads include a "Release_Notes" file in the zip file, it lists all the changes from revision to revision.

Please note that the WYSIWYG HTML editor in PDshop has been updated.  There has been a significant change to the Editor, most users should consider upgrading since the old version's editor may stop working with new Internet Explorer, Firefox, and Chrome updates that are due out.