How to print irule with format in irule editor?

You can archive the iRule to your desktop using the iRule Editor's File > Archive function. It saves as a text document in the Editor's Archive folder (you can set where this is) with indentation still intact. Although it's not the same indentation as used within the Editor itself, it is something. You can open with a text editor.

You can also use notepad++ or sublime text editor with TCL format.