We'll guide you through how to annotate PDFs on your Windows, Mac, iPhone, or Android devices for free, without the need for any additional third-party tools or software.

If you are wondering how to annotate a PDF on Windows, you can use free online tools and software that we have included in this article.

Two weeks ago I asked ProfHacker readers, “How Do You Organize and Annotate PDFs?”, and you rose to the challenge. I can’t recount the entire discussion here (though it’s well worth ...

Learn about a few PDF management and annotation tools for Mac OS X, and suggest your own favorites for this and other platforms.

Learn how to annotate in Google Slides while you present. Make your presentations more engaging, interactive and impactful with this guide.

We've already covered how you can do more with Preview in Leopard, but Mac OS X Hints points out another good one: image annotation.

W3C standard annotation is a fundamental upgrade to the web that will bridge information silos and enable far easier content sharing and reuse ...

Take advantage of data annotations to decorate your models using attribute tags so that your application’s data definition can be managed in a single place.

Better data annotation—more accurate, detailed or contextually rich—can drastically improve an AI system’s performance, adaptability and fairness.