The perfect complement to a note-taking app, Penultimate is a handwriting app that seamlessly integrates across multiple platforms--the iPhone, iPad, and Android, plus Windows 8 is rumored. On your tablet, Penultimate lets you write notes, mark up images, and save them into your notebook. One complaint is that it still cannot import PDFs for markup, which would is why some users have defected to Notability. PDF annotation has to be coming soon. When it does, you can sign your mortgage paperwork without having three stacks of documents. Or make notes right on resumes.