Using assembler service in livecycle process desing

I am looking into the assembler service to flatten a form that is generated using a renderPdfForm process that is populated using xml.

I tried to drag the assembler service into my livecycle process design and connect the output of the renderPdfForm to the input of the assembler service - but it still requires a DDX.

Any good examples or help on how to work with the assembler service in the process design?

I would also like to use it to merge pdfs where I have the pdfs as bytes in java and would like to call a service to get them merged into one.

Everything I look at talk about the DDX but I can't figure out how to do these two scenarios.

Samples tutorials? - anything will be greatly appreciated.

/Chr