I recently did a series of seven tutorial videos on how to use PDFpen for iPad and iPhone. They're now available to watch at the PDFpen website and I think they're pretty good. Looking back, it's remarkable just how much my document review workflows have changed with the arrival of the iPad Pro. The combination of that big piece of glass with the Apple Pencil make it easy for me to review and annotate documents digitally. This is superior to my old method of printing it out and using a red pen and highlighter. Now I have way more annotation tools available and because the product is digital, it is easy to save, copy, and share. Another benefit I've noticed over time is how much easier it is to hold on to these digital annotations. I recently represented a client on a contract dispute and being able to look at my original annotations when the contract was signed last year was helpful.
Anyway, if you haven't looked into digital document annotation lately, watch these PDFpen videos. I've embedded one of them below.