Last year, some new developers joined the iText team. This resulted in a new release that may not differ much from the previous version if you look at the API, but users should notice that some iText functionality now needs less memory and less CPU. iText is having an internal makeover; class casts are replaced by methods returning the correct class, sequences of if-statements are being replaced by switches to improve readability, resources are being freed earlier in the process, and so on.
New functionality includes support for the JBIG2 image format, support for the HR tag in HTMLWorker, a method to add blank pages in PdfCopy, support for actions in FdfWriter, and other enhancements. Read more about all this in the changelog.