Sumatra PDF introduces new features and fixes some bugs and render issues:

• better PDF handling: that means that more PDF files are rendered correctly
• book view is added: in Adobe Reader it is known as Show Cover Page During Two-Up
• new Properties dialog that shows information about the PDF file. Accessible via File/Properties
• new text export feature. Just click File/Save As and select Text documents as file type
• new send PDF file by email. Accessible via File/Send by email
• new zoom shortcuts: Ctrl + and Ctrl -
• several bug fixes

For more information see the Sumatra PDF changelog.