How can I create a smart eSign PDF that gets emailed to the correct signer based on a drop down fiel

I am looking to automate our purchase orders internally.  I would like to create a fillable PDF that a requestor would full out that gets sent to the appropriate staff members based on the users department that they would select via a drop down.  After filling it out and the requestor signing the PDF, i want it send to their manager via esign email.  Can someone point me in the right direction?