Hello everyone. I'm another iText guy... I've been working with PDF in general for >13 years now (wheeze). Over the last several years, I've been using iText almost exclusively and was made a committer a couple years ago.
I started working for a company called DigiDox in Grand Rapids, Michigan... an "all things PDF" production shop that was getting its in-house tools ready to be sold to the general public. We were bought by Adobe (as their only subsidiary, they had previously always brought groups like ours "in house"), sold to ourselves by Adobe under the name "Audience One", bought by Cardiff Software in Cardiff By The Sea, California, which was bought by Verity (Bay Area), which was bought by Autonomy(UK).
I'm the only DigiDox-er left, one of two A1'ers, and a couple dozen Cardiffians.
I started writing Acrobat plugins (C/C++) for Digidox. When Adobe picked us up (briefly), and then in A1 and Cardiff, I worked with "Headless Acrobat" AKA the PDFL (C/C++ again). In Cardiff/Verity I wrote my own Java PDF library to fill in form data, worked with the PDFL, and with an API-clone we replaced it with called PDFLib by Zeon. Somewhere in the Cardiff/Verity time-frame I came across iText, pitched my own PDF library, and rewrote a fair portion of iText's field rendering/flattening code for my own nefarious ends, submitting my changes back to the trunk in One Huge Slab.
NOTE: I don't recommend submitting patches as an outsider to Open Source projects in Huge Slabs. In my (one) experience, the owners stick it on a back shelf until your code is dated enough to need an overhaul and you end up babysitting your own fork. Smaller patches are good until they to trust you enough to make you a committer, at which point you can go hog wild... just don't break the build. That doesn't go over so well either.
At Cardiff/Verity/Autonomy, I use iText to create and manipulate PDF forms (AcroForms to be precise). I also do odd jobs on the side using iText from time to time.