Hi bmkmartin ,
I apologize,applying digital signatures on the Documents with out password is not Acrobat DC. The program is designed in such way.
Also please refer to this Kb artilce specifying how it works :https://helpx.adobe.com/acrobat/using/digital-ids.html
Go to Edit->Preferences->Signatures->Digital IDs & Trusted Identities->More... In the left pane click on Digital IDs. Select your Digital ID. Click on 'Password Timeout' on top of the right pane. It will give you options on how often you should enter the password for this Digital IDs when signing: Always (default), Never (Not recommended), Once per session, Every x minutes.