Your questions are very general with no information on what tables, layouts and relationships you have. I can only make general responses back.
You can "tag" records in one of two ways:
- Store a "tag" value in a field that is part of each selected record. This can be as simple as clicking a check box formatted field.
- Store a list of ID values, separated by carriage returns in global or related field. This is more complex, but sometimes is easier to keep up to date, especially in networked databases.
To insert multiple documents in container fields, create a related table of records and insert a document, or a reference to the document in each record.