Love me some Sumatra, the biggest benefit to me is using it as the PDF previewer engine in windows explorer. 10x faster than the built in or adobe previewer. Takes a little work to do but since I'm frequently scanning through PDFs it was worth the effort.
It depends what kind of edits you're aiming for and what your setup is.
I have opted to go all-in and run Stirling pdf, which is a server solution and then you can do a shitload of things via web browser.
If quick and dirty is fine than inkscape is a surprise candidate - although it's aimed at vector graphics editing you can easily create overlays for PDFs as well.