Generally there is citation / source information associated with every data item on Ancestry. That you can copy freely and it saves a lot of time. Documents themselves might be copied from (using the general rule of fair usage) but entire documents and large chunks of text should be avoided when they will be public such as here in WikiTree unless you get written permission. This is a bit of a grey area since often documents are available other places as being in the public domain. I download material to my personal computer but try not to put documents here from other sites. In my case, since Censuses are a major source and I'm also an Ancestry.com member, I created a little piece of boilerplate saying I'd downloaded the censuses from Ancestry and giving inline information to identify what census page it is. One of these days, I'll start getting the actual citations Ancestry supplies and get rid of the boilerplate.