The Portable Document Format (PDF) is a popular file format for documents. PDF files are a popular document format
for two primary reasons: first, because the PDF standard is an open standard, there are many vendors that provide PDF readers across virtually all operating systems,
and many proprietary programs, such as Microsoft Word, include a "Save as PDF" option. Consequently, PDFs server as a sort of common currency of exchange. A person
writing a document using Microsoft Word for Windows can save the document as a PDF, which can then be read by others whether or not they are using Windows and whether
or not they have Microsoft Word installed. Second, PDF files are self-contained. Each PDF file includes its complete text, fonts, images, input fields, and other content.
This means that even complicated documents with many images, an intricate layout, and with user interface elements like textboxes and checkboxes can be encapsulated in
a single PDF file.
Due to their ubiquity and layout capabilities, it's not uncommon for a websites to use PDF technology. For example, when purchasing goods at an online store you may
be offered the ability to download an invoice as a PDF file. PDFs also support form fields, which are user interface elements like textboxes, checkboxes,
comboboxes, and the like. These form fields can be entered by a user viewing the PDF or, with a bit of code, they can be entered programmatically.
This article is the first in a multi-part series that examines how to programmatically work with PDF files from an ASP.NET application using
iTextSharp, a .NET open source library for PDF generation. This installment shows how to use iTextSharp to
open an existing PDF document with form fields, fill those form fields with user-supplied values, and then save the combined output to a new PDF file. Read on to learn more!
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