What I really love about consulting is the variety of projects that come my way. Recently I was asked if we could create an application for a client which allowed them to fill in a PDF and store the data in a database.
I looked around and found several different libraries for dealing with PDF files, I do not mean to say I did an exhaustive search or trial. Almost all these libraries touted their ease of use in creating PDF documents in code, many offered capabilities of reading the documents but almost all of them failed to load a document created with Adobe Acrobat, opening only older unencrypted PDF files.
The one exception I found was iTextSharp, a library from http://itextpdf.com/ which offers both a commercial version with iText support provided and an open source version available with a copy left AGPL license.
Read more at http://www.codeproject.com/Articles/1032782/Reading-Acrofields-from-PDF-files
This project explains how to read PDF form fields from a PDF document