When changes are made – document them in the Standard. You could also include prior versions that have come before, even if you were not involved. This allows people to know how many times the standard has been improved.
You could document what was changed as an itemized list. I have done this in the past as part of the document, but found that most people never read it. So I just keep a copy of the prior version to use as reference to see what has changed.
I would encourage you to develop a revisions document apart from the standard. You will use it to train your staff on what has changed. Make sure that when you distribute the updated standard that you include the revision doc with it. Since you have developed it,you could include it in the appendix.
Example of a brief list to include in the introduction of your standard:
Version 1 – Initial Released March, 2004
Version 2 – Released April, 2005
Version 3 – Released November, 2007