Ubuntu Guide posted a guide about using KeryX to update Ubuntu off-line using another Windows or Linux PC
If you have an Ubuntu machine without an internet connection,you can try Keryx to download all updates on another Windows/Linux PC and keep the Ubuntu machine updating off-line via an USB.Update Ubuntu off-line via another Windows/Linux PC using Keryx
Keryx is a free and open source tool for easily managing packages on offline Debian based computers including support for Ubuntu and Linux Mint