A: Yes it is possible. There are different constructors in the PDFPrint class to load documents, one of them takes a Java InputStream to read the PDF content from. If you have the PDF document in a byte array, you can create a ByteArrayInputStream and then pass that into the PDFPrint constructor.
Q: Is it possible to send a PDF in memory to a printer using jPDFPrint without saving it first? If so how?