To allow an attachment on an activity type, you'll need to navigate to Settings | Activities and then select the activity you'd like to configure.
You'll notice a check box next to the Attachments section that will allow you to enable this option.
Once selected when returning to that activity type, you will be able to Attach Document using the selection below.
Looking for more information creating and managing activities? Or want to know how to create activity forms? Check out our content below!