Filling In Forms - Adobe ACROBAT READER 7.0 Manual

Filling in forms

If a PDF form contains interactive form fields, you can fill in the form electronically and
submit the form by email or over the web. Reader also lets you spellcheck your entries. If
the form author added special usage rights to the PDF document, you can also save the
form data.
PDF forms may contain bar code form fields that typically appear as a series of vertical
bars with a unique set of characters underneath the bars. You can't manually enter data
into the bar code form field, but the bars and characters of these interactive barcode fields
change to encrypt the data that you've entered into other form fields in the PDF.