How to upload png and pdf files to iCloud?

I have png images on my Mac that I'd like to have on my iPhone. I also have pdfs.

My iCloud is set up so that any photos I take on my iPhone go into iCloud and then Photos on my Mac.

I do NOT want to synchronize Photos to upload to iCloud because I also take photos with a separate camera. I don't want these to go to iCloud because of large file size.

I'm very frustrated by the lack of interoperability between Mac, iPhone, Photos, and iCloud. It really seems I should be able to drag and drop or at least upload any kind of image file from my Mac to iCloud without having to go through Photos.