Mergewell Mail Merge

Use this when the user wants to mail merge from Excel or CSV to PDF: personalized letters from a spreadsheet (thank-you letters for each donor, the same letter to 200 people with their names), certificates in bulk from a name list (award, completion, participation), or envelopes from a contact list (#10 with return address). Fills {{Field}} placeholders with defaults, formats and {{#if}} conditions for each row and returns ONE combined PDF (one document per record, up to 2,000 per batch) plus a per-record merge report CSV. Does not send email, mail, or print anything, and does not make mailing labels. Do not use for Outlook or Gmail bulk email.

Use this when the user wants to check a mail merge before printing: see how their spreadsheet (CSV or Excel) or list fills a letter, certificate or envelope template, which template fields like {{First Name}} have no matching column, which columns were matched by a similar name (first_name for First Name), and which records have empty values. Returns the first 3 merged records (or from preview_from) and a missing-field report; no files. Does not send email, print, or make labels. Do not use for Outlook or Gmail email merges.