svn cat

If you want to examine an earlier version of a file and not necessarily the differences between two files, you can use svn cat:

$ svn cat -r 2 rules.txt
Be kind to others
Freedom = Chocolate Ice Cream
Everything in moderation
Chew with your mouth open

You can also redirect the output directly into a file:

$ svn cat -r 2 rules.txt > rules.txt.v2