Here's a Player Reference Card for Ultima IV that contains information not included (or just not as explicitly laid out) in the documentation GOG offers, including keyboard commands, moon phases, rune translation, and a comparison of each profession's magical ability: http://www.paradroid.net/u4/refguide/refguide.html
It's for the C64 version, but still has plenty to offer.
You can also get the Player Reference Card for the IBM/MS-DOS version, that GOG offers, from here: http://www.abandonia.com/en/games/25548/Ultima+IV+-+Quest+of+the+Avatar.html
Under the "extras", download from the link marked "Player Reference Card". It's in .PDF hehehe
And that C64 version site is a great resource. And even though I've d/led the DOS version from here and added the latest ux4: Ultima IV Recreated
to it, I'm actually playing the Ultima IV Gold
for the C64 instead hehehe
If one is interested in playing that one, I highly recommend playing from/with the .D81 3.5' floppy-disk image copy via the WinVICE64SC emu. That's what I'm doing! hehehe It can be found easily by browsing around the site linked to in the top post in this thread (for which I've given it's poster a "+" hehehehe).