Is there a symbolic meaning of the poem, "After Apple-Picking" and what is the theme?
Yes, there is a symbolic meaning to this particular poem. The poem as a whole symbolizes how the best rewards in life aren't free. We have to work for them, and even though they may be exhausting to accomplish or achieve or attain, they are worth the work and effort.
The main theme relates to Frost himself, it seems. It encompasses references to his own life. For example, Masterplots II states that this poem was published after his first book and it was not received as well as he had hoped, which led Frost to question his future as a poet (qtd. in Enotes). On the other hand, another theme relates to how Frost is ultimately satisfied with his body of work and has accepted that perhaps some works might not sell as well as others.
Another theme deals with life after death. Frost wonders what, if anything, awaits him after death. Masterplots II states that:
In a poem entitled “The Onset,” he uses the cycle of seasons to suggest that death is only temporary, like winter, but in “After Apple-Picking” he provides no such assurances. The early hopeful image of the ladder pointing “Toward heaven” is not confirmed by the conclusion of the poem. (qtd. in Enotes)