How to Mail Merge from Excel (.xlsx / CSV) into Official IRS & ACA PDFs (1095-C, W-9, Form 2848, SS-4) Without Adobe Acrobat

A practical engineering guide to inspecting opaque IRS AcroForm /Fields hierarchies, handling XFA shells and checkbox /AS appearance states, and batch-filling 1095-C, W-9, 2848, SS-4, and 843 PDFs from CSV or Excel.