Having never done this myself, I would look for a utility with a Command Line Interface, like pdf tool kit or ghostscript.  You can build and issue a command to merge the files and then open the resulting file.  We use Bluebeam at work for merging pdf's but it is costly and does not have a CLI.  Someone else, having done this before, may have a better idea.

Sorry it's taken me so long to see this. I sometimes go back and read older threads I missed.

Zachary, Matt's command-line utility suggestion is a good direction. Access can collect the PDF paths from your query and pass them to a local PDF-merging tool, such as PDFtk, to create one new file. For a workplace database, use a tool approved by your IT department and keep the original PDFs unchanged.

The button's basic sequence would be: collect the paths in the order you want, verify the files are accessible, run the merge into a uniquely named output PDF, wait for the merge to finish, check that it succeeded, and then open the result. Quote paths containing spaces. One important detail: VBA's Shell command normally returns before the external program finishes, so don't immediately try to open the output on the next line.

My FollowHyperlink lesson covers opening a PDF in its associated application. That lets the user review and print the merged PDF in their PDF viewer. Access's own report Print Preview is for Access reports, not a viewer for merging existing PDF files.

I'd get two sample PDFs merging successfully outside Access first, then connect that working command to your button.