Paper, like trees, is carbon neutral in the sense that carbon is absorbed then released. Zero net addition to the atmosphere.

Forests can be used to sequester carbon because of the large number of trees continuously in existence even if individual trees come and go.

For paper, the sequestration angle is more dubious but should also be considered based on the total amount of paper continuously in existence, not on the longevity of a single sheet of paper.

you can compost paper, but a lot of it is treated and doesn't decompose very well. E.g. we have a compost heap in our building's garden and someone keeps putting bits of paper bags there, which last years unless you proactively go and try to break them up.

Also, wouldn't composting it release as much carbon as putting it in landfill? And landfills are bad in many ways.

Recycling it seems a better idea.

Removing oxygen prevents decomposition. My home town found out the hard way when they took samples from an old landfill, expecting to be able to build a park over it. Clay layers had been added to prevent runoff into a nearby river, and as a result the newspapers were still readable decades later.