This article says that Orange County, CA is one of only a few that prints it own ballots.
https://www.wsj.com/articles/ballot-printers-rush-to-meet-mail-in-voting-demand-11598002202
"This year we are going to mail probably around 40 to 50 million pieces." said Jeff Ellington, the company's president and chief operating officer.
"There's approximately 200 million registered voters in the country. And we will have the capacity to do approximately 20 million [absentee ballots]," he said.
Not everyone will vote by mail, of course, and some election offices will handle the mailing and printing of ballots on their own. But that still leaves a big gap to fill in a short period of time.
Only 74.56% of Ballots Cast have been reported
https://youtu.be/6R6hxPYWD50