The pH of the leafmould is dictated by the "leaves" used. IMHO if you use solely pine needles, you'll get acidic leafmould, but if it's mixed , it's pretty much neutral. https://www.rhs.org.uk/advice/profile?PID=478
Leathery leaves are best run over the mower first. I do this with sweet chestnut otherwise they just sit there taunting you.As the RHS says, unless you're using all pine needles, you're unlikely to have any problem with pH.