Suppose if we want display contact name on the Sales Order PDF print then we needs fetch it from contact record. Normally up to 3 join are supported on the Advanced PDF template. In order to populate contact name to PDF, please refer following steps
Step 1: Create a custom entity field on the customer record
Step 2 : Add {contact.entityid} in Formula field
Step 3 : Uncheck the Store Value field
Step 4: Save the Custom entity field
Now Primary contact of the customer is populated to this custom entity field. Then populate this field value to Advanced PDF template. ${record.entity.custentity1}, where custentity1 is the field id of the above custom field.