If you were to start eating "an apple a day" (which you should) by the end of the year you'd have eaten around 330 apples. Let's round that down to 300 since it's unlikely you'll eat one every single day.

Now, an average apple has about 5-7 seeds. Let's run with 3 to account for those cut through or shriveled up and the ones you might miss. In total you should have about 900 seeds.
They keep well if first left to dry overnight on a paper towel and then stored in something like a pill bottle. Throw in a silica gel packet to prevent mold.

Apple seeds have a germination rate of about 50% but we can go as low as 33%. One group of 3 would account for a seedling, with 300 in total. With say 2 meters between each, you could cover a surface of over 1000 square meters in one go.

Next winter you could plant your very own crab apple orchard on any sunny site you found on Google Maps and later prospected during your hike. No one will know about them or care but the many animals and insects feeding from it and the animals and insects feeding from them as well. Maybe some long lost traveler. Maybe a platoon digging trenches nearby.