PPX6 would probably work for you if your intended "final destination" was a printed page -- but (a) I assumed you were more screen-focussed and (b) I was trying to find a free solution that I'd be at least reasonably happy to use myself.
Correct, screen-focussed. At that point I hadn't thought as far as PPX6's output, only that it should give very precise control over positioning. It wouldn't cost me any extra
as I already have a copy.
IainB's suggestion of OneNote looks good, but I'm not sure it's an appropriate solution to the problem if it's the only likely use you have for it and if you don't already have an Office license.
I already have a license, and if all else fails it may well do, but I agree that it (and some other suggestions) are getting heavy-duty for what I wanted. I was hoping for something small and simple.
If you already have a PhotoPlus license for pretty much any version at all [...] each dropped image becomes a layer that you can manipulate independently [...]
As soon as people start talking about layers, which I don't understand, the complexity of the software begins to loom large.
(PhotoPlus also has screen capture capabilities, if you're in reductionist mode, although ScreenshotCaptor has elbowed everything else I've ever used for such purposes out of the way!)
At the moment I'm using HyperSnap 6. SSC is complex, and its Ctrl+Z Undo didn't seem to work for me.