How easy is it to auto-populate form data in a PDF? Well, it turns out there's a tool called PDFTk (described in http://www.mactech.com/articles/mactech/Vol.20/20.11/FillOnlinePDFFormsUsingHTML/index.html) that provides the ability to dump the interactive fields into a FDF and load it back into the PDF. The download links don't appear on the main site, but you can go to this link to grab the latest versions.
Ubuntu v12.04 has PDFTk version 1.4, which isn't the latest version. To compile the latest, download the source and apt-get install gcj, which is a Java to native bytecode compiler. Link the Makefile.Debian to Makefile, and run make. At the end, you should have a working pdftk binary!
PDFTk seems to provide a wrapper over the iText PDF library. There is one issue whereby if an owner password is set, you are prevented from opening it (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=531529) The workaround is either to patch the source accordingly (see https://github.com/onehub/pdftk/blob/master/debian/patches/drm_fix) or use qpdf --decrypt to remove the encryption before using pdftk with it.