No Network Access: Sandboxes don't have network access, so if a malicious document can compromise one, it can't phone home.
Dangerzone can optionally OCR the safe PDFs it creates, so it will have a text layer again. Compresses the safe PDF to reduce file size. After converting, Dangerzone lets you open the safe PDF in the PDF viewer of your choice, which allows you to open PDFs and office docs in Dangerzone by default so you never accidentally open a dangerous document.
You give it a document that you don't know if you can trust (for example, an email attachment). Inside of a sandbox, Dangerzone converts the document to a PDF (if it isn't already one), and then converts the PDF into raw pixel data: a huge list of of RGB color values for each page. Then, Dangerzone takes this pixel data and converts it back into a PDF.
The playground allows you to learn about systemd interactively, right from your browser! Create examples without the danger of breaking your system, and without being distracted by hundreds of unrelated unit files.
Cuckoo is a system emulator written in Python for analyzing malware. It automates much of the process of reverse engineering malware samples, such as tracing execution, snapshotting memorry, tracing API and function calls, and dumping network traffic. Generates reports at the end of execution. Modular design, so it's easily customizable.