Whonix ™ protects against the threats outlined below, such as files that inadvertently or maliciously attempt to reveal the real IP address of the user, or third-party, external applications that can leak information outside of Tor. Despite this protection, it is recommended to always follow best safety practices.
Do not Open Documents Downloaded via Tor while Online
The Tor Project explicitly warns against opening documents handled by external applications. The reason is documents commonly contain Internet resources that may be downloaded outside of Tor by the application that opens them. 
This warning is not strictly relevant to the Whonix ™ population since all traffic is forced over Whonix-Gateway ™ and the IP address will not leak. Nevertheless, for better safety files like PDFs and word processing documents should only be opened in offline VMs.
Malicious files or links to files pose a greater threat and can potentially compromise your system. Therefore, follow the wiki advice and avoid opening random links or files in Whonix-Workstation ™. Instead:
- Qubes-Whonix ™: It is preferable to sanitize the PDF [archive] or open the file or link in a DisposableVM.
- Non-Qubes-Whonix ™: The file should only be opened in a separate, offline Whonix-Workstation ™.
Do not Torrent over Tor
See File Sharing.