Adobe Sign
We create forms using Indesign then secure them to allow customers to fill in and sign forms using Adobe Acrobat.
Our customers have signed up to Adobe Sign and use that to send out our forms to request signing but when they come to select the files to request e-signatures, the error message ' This document is a secured filed and cannot be e-signed.' is poplulated. The security settings for the forms don't allow changes but do allow filling in and signing forms.

