The PDFpack product description said explicitly that PDF combining can happen in Adobe Online, AND in Adobe Acrobat DC on my device. See here:
Get online PDF tools you can use in a browser, with Adobe Acrobat Reader DC on your computer, or with the Acrobat Reader mobile app.
However, when I try to merge a PDF on my device, it takes me to the web portal instead of doing the merging in the software itself. I have no interest in having Adobe have access to any files I am merging or my data, in any capacity. I have no interest in giving Adobe the rights to use my data or files once they are uploaded to the cloud. In fact, I do want them uploaded to the cloud at all. What is the solution to this?