If you want to delete a document, log in and go to the archive.
If the document has not been signed yet, you can click the cancel button, meaning that the invited person can no longer sign the document by following the link he received.
After that you can select the delete function. If the invitation has already been signed, you can click the delete button right away. This causes the document to disappear from your archive, but it will remain in the archives of anyone else who has signed it, and remains legally valid.