I'm making some good ol' maps at work (Using 10.x) and I'm having difficulty getting my legend to fit with the amount of descriptive text I have and the amount of space available to me (as well as to make it look… you know… decent. Which can be difficult a lot of the times with how clunky layout view in ArcMap is).
Is there even a way to theoretically get ArcMap to un-gray-out the checkbox that has "Preserve Aspect Ratio" checked? Nothing I have tried has worked and my google – fu ended with someone who had a similar question and a response that was basically, "Sorry dude, ArcMap just be like that some times."
Ideally I would rather not convert the legend to graphics since you can't make changes easily to the legend after the fact, so is there a better way to do this without converting to graphics?
Here's a picture if it helps refresh your brain on where this is in the legend properties: 
Best Answer
You must check fixed frame as pic shows to be able to resize legend and change aspect ratio
once you check fixed frame, the 'preserve aspect ratio' option is no longer grey out, as pic shows.
now you are free to drag to resize the legend ( aspect ratio will change when you drag )