iText 5.4.4 introduces functionality that was long awaited: PdfCopy is finally able to merge AcroForm-based interactive PDFs. This is a huge step forward for people who want to merge accessible forms, preserving the accessibility.
At the same time, we deprecated the PdfCopyFields class. As opposed to PdfCopy, this class allowed you to merge forms, but this didn't result in a tagged PDF: all structure was lost.
As always, we've been fixing a number of bugs, or rather: we've improved iText so that (1) it now deals with some image types that previously weren't supported, and (2) when confronted with an invalid PDF, we try throwing a meaningful error instead of an ordinary NullPointerException.
Read more on our blog.