Copy work usually needs a higher contrast film than general pictoral photography to get similar looking results so you might be better off with something like Velvia for it's contrast boost. Keep this in mind if your chosen film gives you flat looking results and you decide to reshoot. Sunlight should work just fine, just be sure there are no strong colored reflective surfaces nearby to taint the light quality. A polariser would be a good addition to remove glare from the copywork.
Good Luck!