PDFpen provides many options to access and open a document for editing.
Upon launching the application, PDFpen opens into Apple's native Files view. Select a document for editing. Opening a document from Files means your changes will stay in sync as you edit.
Switch between iCloud and Files-compatible apps, such as OneDrive and Dropbox, in the Locations column on the left side of the Files view. Then navigate into your folders and tap on a document to open it.
Create new folders, delete, manage and move documents between folders just as you would in the Files app.
Navigate Document Views
Apple's Files view provides several options for searching and sorting your documents. Sort by Name, Date, Size, Kind, or Tags. View folders and documents as a list or as thumbnails.
To import a document, or create a new one, tap “+” or “Create Document” respectively. Tap “Select” in the upper right to share, delete, or move documents.
There are a couple ways to open a PDF from another application in PDFpen, aside from using the Files view.
Use Open In…
Web: In Safari, when viewing a PDF, tap it to see a menu bar appear along the top. Tap in the upper right. Tap “PDFpen” from the list of available apps.
Email: In Mail, tap and hold the icon for a PDF attachment. From the menu, tap “Open In PDFpen” from the list of available apps.
Tap on a document to open it up. Tap one of the markup tools in the toolbar to quickly add a highlight, a handwritten note, or a comment. See The Toolbar for more on markup tools.