iCloud is Apple's cloud storage service. iCloud stores music, photos, documents, and more and wirelessly pushes them to Mac and iOS devices. See Apple's website for more information about iCloud.
You'll need to have PDFpen (or PDFpenPro) 5.7 or later. You'll also need to set up your iCloud account.
If you purchased PDFpen or PDFpenPro from the Mac App Store, that's all you need.
If you purchased PDFpen or PDFpenPro from Smile directly, you'll also need to purchase and install PDFpen Cloud Access, available on the Mac App Store for 99 cents.
Currently, Apple only allows iCloud access to applications purchased on the Mac App Store. PDFpen Cloud Access, available on the Mac App Store for 99 cents, works with PDFpen and PDFpen Pro to make iCloud documents available to users who purchased the license from Smile.
PDFpen from the Mac App Store comes with iCloud enabled, and does not require PDFpen Cloud Access. You have the same iCloud functionality in PDFpen when purchased direct if you also purchase PDFpen Cloud Access.