In order to sign document with visible signature we have very bad solution at the moment: passing a PDF as an InputStream that serves as a template for the appearance settings is very inconvenient. So, Now Everything is well and fixed! You only set image with location, zoom, width, height, and etc, and everything will be added automatically. I've just already done this, and I will upload my patches too. I have wrote example too, in order to see how to use it. Everything is easy!
PDFBOX-1261 Support for visual signature without a pdf template