I have used a lot of PDF mark up apps, and I used PDFpen in the past too. I only went back to it because I bought a Wacom Fineline stylus to get me by until my Pencil came in and this was the only PDF mark up app that was compatible. Every day in my job I need to mark up PDFs and writing on them is the quickest way for me so I thought even the $20 for the app would be worth it for the 4 weeks it was going to take to get my Pencil it would save me a lot of time, and maybe they fixed PDFpen in the second go around. I am sad to say it is still as unusable as before. The stylus does connect but the app crashes for other unknown reasons, the UI in the app is clunky, nothing about using this app is fluid and just left me frustrated and moving away from using it after an hour of trying to get used to it.