In generally, you have no need to update Bios, so there is no tutorial for updating Bios now. You can refer to the tutorial "How to flash BIOS for Chuwi Dual OS Vi10 - 32G" http://forum.chuwi.com/thread-237-1-1.html
the document for the BIOS flash tutorial you mentioned (for the VI10) is empty.
Please take your time and compile a usable BIOS flash tutorial.
It would be the best if it would be a tutorial in HTML (with pictures) or Text File. Word and PDF Documents are insecure.