Thank You
PDF to TIFF is certainly possible. But it kind of depends on what is in your PDFs. You can go directly from a PDF reader to a TIFF writer, if your PDF only has an image (JPEG) on it. Can you provide some sample data to better illustrate what you're trying to achieve?
In terms of the overall process, I would first focus on getting your PDF to TIFF conversion process working the way you want, and then tackle the workflow of finding the files in all your folders and feeding them into conversion part.
Attached is a sample of an as built drawing that we are trying to convert from pdf to tiff.
Thank You
Provided all your PDFs are raster based like your example, this should work. You'll need to set the folder(s) that you want to look in (with subfolders) for the Directory reader and set your output folder as well on the writer.