How to create a Document Template for "Scanned" PDFs? (Editing isn't necessary.)

I have a Custom Content Type called Vendor Invoices. It is based off the Document Content Type. I would like to create a Document Template that will support PDFs, but the PDFs should always be added via an "upload" (since these are Invoices that we will be "receiving", there is no need to actually "Create" one). So, I don't need to support New Document or the Drag and Drop" "New Document. I simply need the users to "Upload" the documents. Although, I have created several Columns for this Content Type (Invoice Number, Invoice Date, Vendor Name, etc) that the user will input when uploading the Invoice (PDF), so I WOULD like the Document Information Panel to appear. Is that only possible by using one of the Office document types?

Any thoughts or ideas on how I might accomplish this?