One workflow to join docs and pdfs to one big pdf

Hi! I've been trying to do something that, until now, just hasn't worked.

I have a bunch of word docs in a folder and I want to convert them to pdf and join them together. I have no problem with that. But, can I use the same workflow to join pdfs together that were not word docs to begin with? An action to "ignore the conversion" if the file is already a pdf.

Furthermore, can I grab a bunch of docs and pdfs and join them in one giant pdf so that the docs will be converted and then the multiple pdfs joined with just one workflow?

If so, how?

Thank you very much.