The PDF is one of the file types I interact with frequently for work alongside word processing documents, spreadsheets, audio, video and images. This app lets you mark up PDFs via touch or mouse. Let the page bleed with red ink: you can highlight, chicken-scratch and strike-through to your heart's content. On my touchscreen ultrabook I found the experience a bit awkward. It helps to have a light touch when making marks and the interface and responsiveness could use some work. I imagine the experience improves on the Surface Pro or other Windows 8 tablets. Nonetheless, for the price this app was a no-brainer for me to make my touchscreen more usable.