PDFItems + Additional Resource Plugins

I am trying to implement the PDFItems plugin on our Omeka install (v2.7.1, classic) @ cannabismuseum.com/omeka. Goal is to add an export label button to each items page.

Essentially, add a button on each item page that will generate a PDF file formatted to our specs. I have the PDF generation and formatting handled, and was hoping the PDFItems plugin could be able to establish the export button on each item page. From there I was hoping to modify the PDF writer using code borrowed from Reports Plugin. For more on that modifications, see Topics 1 and Topic 2.

PDF Items requires AdditionalResource plugin - which is not installing, Omeka states “not a valid plugin” - any insights? Is it a versioning issue? Is there any work around?