AFAIK the docs don't cover PDF forms (or AcroForms or whatever Adobe calls them now).
More of an iText question really as there's no in-built functionality in Seam for this. Read the iText docs
Here's a basic code snippet that will get you started:
PdfReader reader = new PdfReader("input.pdf"); PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("output.pdf")); AcroFields form = stamper.getAcroFields(); form.setField("SOME_FIELD", "Hello!"); stamper.setFormFlattening(true); stamper.close();