Natural Docs requires Perl 5.8 or higher to run.  If you’re using Linux or Mac OS X, you should already have it.  If you’re using Windows and haven’t installed it yet, you can get ActiveState’s ActivePerl for free.  There are free versions available for many other platforms as well.

• Create a folder for Natural Docs and unzip the downloaded file there.  The zip file will not create its own top-level folder.
• On Windows it should be ready to run, though if you get error messages you may need to edit NaturalDocs.bat.  See the troubleshooting page for details.
• On Linux you need to apply the execute attribute to the NaturalDocs file, such as with “chmod +x NaturalDocs”.