Pennsylvania courts generally hold that posting is required to exclude
hunters. See, e.g., Commonwealth v. Sweeley, 29 Pa. D. & C.4th 426, 433
(C.P. 1995) ("Open lands that are not posted or fenced off are presumed
open for recreational use by the public, especially in rural counties
where hunting and outdoor activities are common.").
[i]
f. . . it is the custom in wooded or rural areas to permit the
public to go hunting on private land . . . , anyone who goes hunting .
. . may reasonably assume, in the absence of posted notice or other
manifestation to the contrary, that there is the customary consent to
his entry upon private land to hunt or fish." \l "F90"

I live in Centre County, PA, and have always assumed that if I don't
see a NO HUNTING or NO TRESPASSING sign, I can hunt on that land.
Provided it's in the country and not obviously a home area, of course.

I've never had a problem.

. Signs must be placed on their own standard, not on trees or posts.

I would estimate that 99 and 44/100 % of the signs I've seen have been
on tree trunks.

vince