The Pro version adds these additional features that the regular version does not:
Create cross-platform fillable PDF forms
Add interactive signature fields to forms
Create and edit Table of Contents
Convert websites into PDFs
Correct typos in OCR text layer
Add and edit document permissions
Automatic form creation - detects text fields and check boxes in existing PDF and makes them fillable
Create submit buttons to submit form data via web or email
Gather submitted form data via backend integration
Export in Microsoft® Excel (.xlsx, .xls), Microsoft® PowerPoint (.pptx, .ppt), and PDF Archive (PDF/A) formats (requires Internet connection)

Features of PDFpenPro
Add text, images and signatures to PDF
Correct text in original PDF with editable text blocks
Fill out interactive PDF forms and sign them
Redact or erase text, including OCR text
Search and redact text; search and replace text
Export in Microsoft® Word format
Scan directly from Image Capture or TWAIN scanners
Perform OCR (Optical Character Recognition) on scanned documents
Viewable OCR layer for proofing OCR text from scanned pages
Adjust resolution, color depth and contrast, skew, and size of an image or scanned document
Sign PDF forms via interactive signature fields (not digital signatures)
Insert and remove pages; re-order pages in a PDF by drag-and-drop; combine PDFs
Move, resize, copy and delete images in original PDF
Save PDFs directly to Evernote
Copy and paste rich text; retain fonts and formatting when copying from PDFs, including columns
Context-sensitive popup-menus enable quick edits
Add (and print) notes and comments
Mark up documents with highlighting, underscoring and strikethrough
Save frequently-used images, signatures, objects and text in the Library
Apply business-related and sign here stamps via the Library
Print notes and comments with or without the original text
Print a list of all annotations along with the document
Full screen mode, as well as zoom to document width and zoom to actual document size
Password protect a document with up to 256-bit AES encryption
Compatible with iCloud Drive
Sync Library items with PDFpen for iPad and iPhone via iCloud
Automate PDF manipulations with AppleScript
Available in English, Japanese, German, French, Italian, and Spanish

Requirements: Intel, 64-bit processor, OS X 10.10 or later
Home Page - https://smilesoftware.com/PDFpenPro