Need an app for reading, annotating, or creating PDFs on iOS and Android? I've got five great ones -- every one of them free.
This free PDF tool for iOS and Android goes well beyond mere PDF reading. It lets you fill in and save PDF forms, and has a variety of commenting and markup tools, depending on the platform. The Android versions includes annotation tools such as pencil, note, and highlighting, while the iOS version had a variety of advanced PDF commenting tools. There's lots more as well.
This one is for the iPad only. It offers pens and highlighters for annotation, and the ability to add notes to PDF documents. You can draw and write directly on the PDF using your fingers, and a unique software-based palm rest lets you rest your palm on a PDF without marking up the document. The only drawback: The app includes ads.
This iOS-only PDF tool lets you read, annotate and edit PDFs. But that's just a start for what it can do. It also lets you have threaded conversations as you mark up PDFs, making it an excellent collaboration tool. Among its annotation tools are underlining, crossing out, and freeform writing.
Here's an Android-only PDF tool that opens PDF lightning fast, includes great zooming and searching, and has a very comprehensive suite of annotation tools. It's also great for organizing PDF files, and lets you create different categories for finding them. Its search is particularly useful, and lets you search not just for local files, but also on the Internet simultaneously.
For maximum compatibility with reading any PDF document, you can't go wrong with the mobile version of Adobe Reader, for both iOS and Android. It lets you fill out forms, sign documents, and make comments on them. It might not include all the bells and whistles of some competitors, but it's safe and solid.