You have to test your writing on your audience to ensure that you are in fact communicating effectively and efficiently.
The absolute easiest test to implement is just listening. Train yourself to keep your ears open when you are out and about in the library. Train your staff to do the same. Make mental notes when you hear someone making comments or asking questions regarding your writing. Tell your staff to do the same and to pass that information on to you.
When patrons are filling out forms, do they complain? Do they ask for clarification on what is being asked of them or where to place specific information? If so, take another look at the form and determine if it can be modified to solve the problem.
When possible, ask questions to see if you can pinpoint which part is problematic. Patrons generally don't mind answering your questions if they feel they are being heard and their thoughts might be helpful.
All writing can be edited.
There is a feature within Microsoft Word that will assess your document's reading level. It is not automatically available on the Ribbon, so you will have to search the Help feature for "Check Readability" to get details on how to set it up.
Once it is activated, the Editor will give you options as to what sort of writing you are attempting. Choose "Casual" to make sure your document covers the widest audience. The tool will then give you an overall readability score as a percentage (the higher, the better) and will walk you through some of the "errors" it thinks could make the document more readable. It isn't perfect, but it does give some really good suggestions on things you may have overlooked.
The Editor will also give your document an overall Flesch Reading Ease score, a Flesh-Kincaid Reading Level score, and the percentage of passive sentences used.
You are aiming for:
Flesch Reading Ease ~70-80
Flesh-Kincaid Reading Level ~ 8
Passive Sentences % - As low as possible