I have Limited traffic - how to update avast offline?
If the system you want to update off-line, you may still have to have an internet connection depending on the OS.
Whilst Asyn gave you a link to get the full off-line installation file, you may still need an internet connection. For those that have XP (and possibly Vista) may require a connection to download an element that isn't present in the off-line installation file.
EDIT - Note: If by "I have Limited traffic" you mean a slow internet connection or dialup, etc. You could try and get a friend to download it or use a Library, etc. to download it.