I used Tenancy Compliance Service to serve my tenants their required tenancy documents and now need to prove that I have done so. Do you keep a signed copy of the document on file?

Yes. You can download a copy of your Tenancy Compliance Service documented by logging into your Upad account, going to your Property Console and clicking on the Details Tab for the property you wish to download the Tenancy Compliance Service document for, under the Tenancy Compliance Service section.