The poem begins by establishing its focus on paper (and thus putting the title into context). Though it isn't explicitly said that this is the case, it seems like the speaker is holding paper in their hand, contemplating what this humble material says about life, society, and humanity. The speaker perceives a kind of power in the paper, saying in line 3 that this "is what could alter things." Paper could change the world, somehow, though the speaker's meaning is still to be explored.
Light functions as a symbol in this poem. Traditionally a symbol for human knowledge (which, in the poem, depends on paper), it also suggests the fragility of that power—after all, paper is thin enough for light to pass through it! The enjambment between lines 1 and 2 after the word "light" visually represents the translucence of paper, as if light shines through the line break.
There is also a delicate consonance at play in these lines (and throughout the poem) which suggests the fragility of paper (and, by extension, human life):
Paper that lets the light
shine through, this
is what could alter things.
"Things" here is an ambiguous word, but it allows the poem to set itself up on quite general terms. Indeed, the poem's subject is both specific and extremely broad: paper on the one hand, and nothing less than the meaning of life on the other.