: You can use the Nitro Migration Assistant to move your library items, stamps, and user preferences from PDFpen Pro 13.1 to the newer Nitro version. Key Updates from Version 13.1
If you are updating to 13.1 from an earlier version, this build included several significant enhancements: PDFpen Pro 13.1 fix
For users still on version 13.1, several common stability and performance "fixes" have been identified: : You can use the Nitro Migration Assistant