You've changed what was an excellent iOS 12 pencil behavior for PDF markup in iOS 13/iPadOS. You used to be able to scroll PDFs with your thumb while drawing with the pencil to mark-up PDFs. When one would lift the pencil one could continue to scroll without having to "toggle off" the markup icon (top right).
In iPadOS the Apple Pencil activates PERMANENTLY the markup feature, and now, when I try to scroll with my left thumb, I unintentionally draw lines on the PDF instead of scrolling. As a user, I now have to constantly toggle off the pencil icon so I can continue to scroll the document, resulting in a terrible user experience for those of us who purchased the iPad to work on large documents digitally with the pencil.
Please revert back the pencil behavior for PDF mark up as it was in iOS 12.