: 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
For users still on version 13.1, several common stability and performance "fixes" have been identified: PDFpen Pro 13.1 fix
The software previously known as has been rebranded and updated to Nitro PDF Pro following Nitro's acquisition of Smile Software. If you are experiencing issues with version 13.1, the primary "fix" recommended by the developer is migrating to the latest Nitro-branded version. Resolving Issues in PDFpen Pro 13.1 : You can use the Nitro Migration Assistant