You can use Acrobat to edit forms using the Advanced Editing
tools available under the Tools menu.
However if you choose items from the Forms menu or toolbar then
you will probably find that you end up editing your form in Adobe
LiveCycle Designer rather than Acrobat.
Adobe Designer is an application which comes with Acrobat Pro.
It uses PDF as an output medium. However the way that Designer
operates means that forms created by Designer are fundamentally
different from forms created by Acrobat.
For example an Acrobat created form typically contains a
background and then a set of fields. The fields operate separately
from the background.
Adobe Designer created forms do not make this distinction. They
use a separate data store to specify the fields. The PDF content is
merely the visible rendition of this field specification. The
underlying field specification is made up of chunks of XML embedded
in the PDF. This XML format is known as XFA - Adobe XML Forms
XFA is referenced in, but is not part of, the ISO standard for
Because Designer documents are PDF documents you can add content
to them using standard ABCpdf methods of adding PDF content.
However if you then open them then in Designer the content will
most likely be deleted because Designer will recreate the PDF
appearance using the separate field specification.
Equally because the PDF output is merely the visible rendition
of a separate field specification the fields and background may be
tied to each other. So you might use ABCpdf to delete a field and
find that the border has been left behind.
In extreme cases the LiveCycle documents may not even contain
any useful PDF content. Instead the PDF becomes a placeholder which
contains an XFA document. The document is only really a thin PDF
wrapper around XFA data. You will find that many PDF viewers
(including Acrobat Reader X and earlier) cannot display this type
of PDF properly.
If you have input to the document creation process, using
LifeCycle to save the file as "Adobe Static PDF Form" may help.
If you want to modify forms you will generally find it easier to
work with Acrobat created forms than Designer created ones.