Alt-right star Milo Yiannopoulos, a moderator of the subreddit, asked Trump how he would deal with H-1B visa abuse in a question that referenced one-time Nazi rocket scientist Wernher von Braun and Trump's wife Melania.
A self-employed redditor asked how Trump would ensure that health insurance would be available and affordable to young Americans.
"One of the first things I will do is to repeal and replace disastrous Obamacare," Trump said, adding he would create a new plan that would increase Americans' choice in insurance.
Another redditor pointed to the length of time since Hillary Clinton's last press conference.
Trump said Clinton couldn't explain her missing emails, nor her positions on Libya, the Trans-Pacific Partnership, or Syrian refugees.
Another user asked Trump which US president he admired most.
"There have been many amazing Presidents in American history, including George Washington, Abraham Lincoln, Dwight Eisenhower and Ronald Reagan, all of whom I greatly admire."
One person asked what Trump would say to Bernie Sanders' supporters.
Trump said he expected millions of Sanders voters would not support Clinton. "We welcome with open arms all voters who want an honest government and to fix our rigged system so it works for the people."
"Hello Mr. Trump, Are you getting tired of winning?" another asked.
Never, Trump said.
One redditor asked what Trump saw as the greatest issue for young Americans.
Trump pointed to a lack of opportunity. "It's a total disaster!" he said. "I will create millions of new jobs, reform our education system, and work to free young Americans from the awful burden of debt."
A Libertarian voter asked how Trump could win over people who were considering third-party candidates, such as Gary Johnson or Jill Stein.
Trump again described Americans' frustration with a "rigged" system. "They know I will fix it so it works for them and their families," he said. "Hillary Clinton's message is that things will never change. My message is that things have to change, and they have to change right now."