Refine usability and experience in repetitive mandatory task

We have a requirement for an app in which the user needs to visualize a document, sign it and visualize it again with the signature on it. The problem comes when the process generates multiple documents.

Since the product has a hardware problem that makes signing very difficult the option now is to re-use the signature in every document generated, but in order to stay "in the law" (it is a financial product), the user needs to be able to actively approve or disapprove the reutilization of his signature, and obviously be able to review every document individually before and after they have been signed.

Any idea?

More info > it is navigated through a 21 inches touch display Right now the user cannot sign directly on the document, we show the doc through pdf viewer and display a dedicated space for the signature, after that the document is reloaded with the signature placed on it.