Related Questions:
Use Custom Fields in my Documents
Auto-populate my Documents with Custom Fields
Make Custom Fields Merge Fields
Answer:
Yes, The Custom Fields you create in Event Temple can be used as Merge Fields in your Documents and Emails.
First you'll need to follow these steps to create your Custom Fields.
Once you are at the field creation screen, fill out the Merge Field Name field with a name that represents your field.
Once you save your new field, open a Document or Email and insert the Merge Field into the text body. Click here to understand how to use Custom Fields.