Not sure if this belongs in #C29HQS63G or #C466X49JB so I will ask in both. I am trying to make a custom pdf which will essentially be identical to a packing slip but it will be get the data from a few item fulfillments instead of just one. What is the best way to go about doing this? I see in the help center that I can create a advance pdf template and populate the data from a search. Is this my best option?

Think of the process as similar to a Word merge operation where you have a template and you source the data. For this you can created your advanced PDF template and then create your saved search and use the N/render module to accomplish the task. In help search for Render search results into a PDF file