How do I change the terminal font?
I found two ways for changing font size in JuiceSSH.
Use Volume keys
The very first time you would've used JuiceSSH, you might have come across this brief tutorial:
(Click image to enlarge)

Use the Volume Up/Down keys to adjust the size of the font.

Traditional way (Settings)
On the default page of JuiceSSH, go to Settings → Font size → adjust it.