That is a big fat NO, unless you happen to know of someone who has a technet or MSDN subscription (or...).
http://windows.microsoft.com/en-us/windows-8/upgrade-product-key-only
That is the link you go to when you need to re-download win 8. Notice, they added a win 8.1.
Problem is, your win 8 KEY won't work with it!
MS purposely won't allow you to have a ISO for 8.1 if you have win 8 installed for whatever stupid reason they can come up with, they want you to use their store.
Makes no sense at all.
If you have multiple machines, then you must download it for each machine.
If something happens, and you need to reinstall. Well, reinstall win 8 first, then again, get 8.1 through their store, and apply it.
They rather have people find win 8.1 ISO on their own (just make sure the hash matches what MS shows on their MSDN site) and use that with a win 8.1 temp default key as was pointed out earlier in this thread.