I'm not happy with this product, I got the pro version for my iMac and the PDFpen on the iPad. Previously, I was using Skim (free on the Mac and very good) and Good Reader on my iPad (also very good), I just thought having two products from the same company might be more similar to each other and work together better, than two separate products. However, the version on my iPad keeps crashing when I try highlighting, it's completely unusable. The version on my iMac is displaying blank pages sometimes, which aren't displayed in Skim (Skim displays them properly). I've gone back to using Good Reader and Skim, at least until they update the PDFpen products to actually work for me.