Can't Resize Artboard Freely in Illustrator 2025

The Large Canvas option that Bobby mentioned is only available when you create a new document.

You cannot create artboards larger than 227 inches in a regular canvas document and you cannot convert a regular to a large canvas document.

Adobe Illustrator has always had upper limits for canvas sizes. By the way, all vector graphics applications have canvas size limits; none offer unlimited canvas sizes. When Illustrator was based on Postscript the size limit was around 120" X 120". The change from Postscript to PDF with Illustrator 9 bumped the canvas size limit up to 227" X 227". That was 25 years ago. It has already been 5 years since Illustrator's large canvas mode was introduced with version 24.2. That mode merely does some internal trickery to make artboards up to 2275" X 2275" possible.

What is preventing you? What difference between versions are you experiencing?