For example this actually happened to me. Psycho landlord prints out unusually drafted lease agreement and send to me as PDF. I read it and am in fact perfectly happy to sign it because it appears to reflect our agreement as discussed and in good faith.
I print it in duplicate but neither of the copies are stapled.
Digitally sent copy is no longer accessible as we both changed phones.
We both sign the final/signature page of each copy and she takes her copy's signature page, but leaves the rest of her copy and the whole of my copy with me saying she just needs the signature anyway.
Then let's say I'm illegally evicted and need to prove my tenancy in local county court. The pages are all loose and she goes to court with a contract that says completely different things which she has happened to collate with the other loose signature page. We each claim the other person's version of the "signed" contract is fraudulent. How is this adjudicated?