Most people coming to eForms will be coming from an HTML
background. There are subtle differences between the PDF form model
and the HTML form model that can cause confusion.
In HTML, a form is part of a web page. Each field in the HTML
form has a visible appearance on the page (with the exception of
hidden fields). So the concept of a field and what it looks like on
the page is pretty much identical.
eForms separate the idea of a field from its visible
Each page of the document owns a set of visible annotations.
There are lots of different types of annotation, but the ones that
are used in eForm fields are called widgets. A widget contains
properties that allow a PDF reader to display it appropriately on
Each document owns a tree structure of fields which spans the
entire document. Each field has a name and also a full name (like a
file path), which tells you how to get to that field from the top
level of the tree. The leaves of the tree contain the visible
widgets that you see on the pages. Note that PDF does not require
that full names be unique.
So there are two independent sets of entities, each with its own
features. The bits you see and which people normally call fields
are in fact widgets.
Widgets don't have a name or identity as such - it's just that
they may be associated with a field which has an identity.
Similarly, a field doesn't exist at a location or on a page it is
just that it is associated with a widget that exists at a
particular location on a particular page.
ABCpdf hides these distinctions from you. When you ask for a
field by name, it will return you the widget associated with that
field. Given the widget, you can find out where it is physically
located in terms of page numbers and page rectangles. Similarly, if
you have a widget, you can ask it for a field name. Behind the
scenes, ABCpdf finds the field associated with the widget and
returns you the field name.