I understand you'd like an offline version of the Spine User Guide for when you're traveling. Unfortunately, there isn't a PDF version of the user guide available for download. The Spine User Guide is only accessible online at:
https://esotericsoftware.com/spine-user-guide
However, you could consider using your browser's built-in functionality to save the web pages offline for later viewing. Most modern browsers allow you to save complete web pages (including images and formatting) to your local drive, which you could then access without an internet connection.
