1. Activate Form Workflow Plus
2. Start G Merge: Mail & Doc Merge with Attachments => Link to install
3. Set up G Merge => How to use
4. In the Settings crank wheel menu of G Merge add a filter selecting your Criteria header column Equal to Approved
4. GENERATE your merges Now or set it to run automatically Every hour or Daily.
NEVER choose On form submit to generate your merges this way. Form Workflow Plus must complete a process before G Merge can run your mail/doc merge.