The answer to this question is a definite No!
The process of altering a Will is quite complicated. A Will cannot be altered after it has been signed and witnessed otherwise it may be deemed invalid. You can alter your Will prior to signing it however all changes must be initialled by the testator (will writer) and witnesses. With an online legal will it is much easier to make the changes and then print a new copy to be signed with two witnesses. You can however go through the process of executing a document called a Codicil. This document allows you to change details in your Will such as an executor or a beneficiary changing their name.
This process is quite involved and can lead to disputes. If you wish to change your Will it would be cheaper and much safer to write a new one.