I hope you are using the free edition of Avg.
This is the site link
As far as updates are concerned, Yes, you can easily update it manually. In the website, on the left-hand side corner, follow I need help ==>Get AVG update.
Here you can see the latest update available for download (~ 5 mb).
Download it to your system. Start AVG. Click on update option. It will give you choice of update through a local folder. Select it and browse to the folder you have saved the update. Thats it!
Hope this is helpful
Sorry to edit , but Avg 7 freeware is also available.