Answer
In practice, this usually means adding three layers around the existing application: a capture layer that pulls in scanned paper, email attachments, or system-generated spool files; an index layer that tags each document with the same key fields the core application already uses, such as PO number, vendor number, or order number; and a workflow layer that routes documents for approval based on rules the business already follows informally. The IBM i application keeps owning the transaction and the data of record, while the document layer makes the paper and PDF side of the process searchable and trackable instead of sitting in file cabinets or shared drives.
Integration approach matters more than most buyers expect going in. Some products tie into the existing application through database triggers or APIs that read key fields directly from Db2 for i tables, which tends to be more reliable long term than screen-scraping 5250 sessions to capture index values. Buyers should also decide early whether document access will ride on existing IBM i user profiles and authorities or run through a separate security model, because reconciling two permission systems later is a common source of access-control gaps.
The clearest sign a project is staying appropriately scoped is that the core application's screens and logic do not change at all. If a document modernization effort starts requiring modifications to the underlying RPG or COBOL programs, it has quietly become a bigger project than originally sold.