Full Use Case:
On the Lead object I have a date field and I want to update this field whenever a Document Action is fired. I tried to use my formula field to merge TODAY() date into the ‘Field To Update’ value in document action but it doesn’t work. How can I get this to work?
The ‘field to update’ value on document action is only text value so you cannot write formula’s in there. You can update another field, then create a workflow to set the date field with any formula you want. The most common use case of this ‘field to update’ feature to update a Status picklist field. Then you can build workflows off that status picklist field changing for example like updating a date field.