I got a Surface Pro and I am also going to use it for reading A4 documents, as well as magazines like the economist and national geographic.
Adobe Acrobat I did not like for reading magazines in full screen controlling it with the touch screen. From some searches over the internet I came across Sumatra PDF and indeed it is usable.
Do you know of a better software for reading A4 pdfs in windows?
Did you try Edge ?

I don't much like it as a browser, but quite like it as a viewer.

BR
I use Sumatra for PDFs, for manuals for appliances and whatnot, and occasional testing to see how an epub looks with it.
After looking around and doing test, I believe Sumatra PDF while not perfect is the best software for this specific use (reading A4 magazines in windows touch screen tablets).
I will continue using this until something better comes along.