Marvel Comics released a free digital comic book on President's Day called Gettysburg Distress. Click the "Open" graphic on the Marvel site to view the comic.
In this short bit of a booklet, Captain
America tells Spider-Man how he traveled back in time to witness Abraham Lincoln’s Gettysburg
Address.
This isn't available as a download, but the Marvel comic viewer works pretty well. Every now and then, it may ask you to sign up. But this comic is free, so no need to sign up. Just refresh the page and all should be well again.