Represents the form and fields associated with this document.

The PDF specification makes a distinction between a field (in terms of a named value) and the visible appearance of the field on the document.

In general, one field will have one visible appearance on the document. However, it is possible for a field to have multiple or, indeed, no appearances on the document.

For example, a Radio Button group encapsulates one value and is represented by one field. However, each radio button has a separate appearance on the document. So one Radio Button field is likely to have many appearances.

For this reason, fields exist within a hierarchy. Each field may or may not have a visible appearance. Each field may or may not have children. These children may be fields themselves and again may have their own children.

Fields are generally referenced by fully qualified names. A full name describes a path down through the field hierarchy - using periods as delimiters - to a specific field object. For example, the name 'person.address.city' would reference a field with a partial field name called 'city' which has a parent called 'address' which has a parent at the top level called 'person'. You can resolve a fully qualified name using the Item property.

Once a field has been obtained, you can query or change its values. If you wish to convert the fields into a permanent part of the document, you can use the Stamp method to permanently emboss them.