PIN protected signature image for sign and fill

Is there a way to PIN protect my signature image in sign and fill? I was using my signature image for everything during the shutdown and it completely streamlined my invoice approvals. I am a government fleet supervisor and have to approve/sign invoices for received parts and services. Now that the shutdown has been over for quite a while my CFO is not allowing me to do this anymore since my signature is not password or PIN protected. He is afraid someone might be able to access my computer during moments I am away from my desk, and fraudulently sign on my behalf. I have always received my invoices digitally, so now that we're back to the "old way", I have to print them out, hand sign them, and scan them back in to send to accounts payable, which is a COLOSSAL WASTE of paper and time.  Please help!!