sumatrapdfreader
Save As > Save Copy (3.6.17065)
Save As is actually Save Copy since it doesn't change the item you're working on.
So the menu should either conform to normal naming (as I've experienced it) by being Save Copy, or it should actually do a Save As and change the location of the active document.
This proves an issue when you are annotating and saving.
Hmmm Save As was a traditional ability to allow for multiple actions. Thus Historically the PS or CBx or edited SMX (others?) save As PDF or TxT so what has happened is nearly all of those functions depreciated and perhaps now there are none to need the conventional As but it is still conventional for changing the location and filename .
Oh wait... I've tried it again and it moved it when Save As'd, whereas before it hadn't (I had even double-checked) - I will have to come back to this if I spot it doing so again...