Its interface isn't as advanced as the native client, but it still has some interface that needs explaining.
One note I found was that the chapter headline (Chapter 9. ThinLinc Web Access) should contain an introduction like the text in 9.1. Overview. My suggestion is to remove 'Overview' subsection and make 'Requirements' the first subsection of this chapter.
Perhaps all chapters should have introduction text. As of right now, it's very mixed whereas some chapters have it and others don't. To have more consistency throughout the documentation this might be something to fix.
Besides what I mentioned in the previous comment, the documentation looks good. It seems to cover everything on how to use Web Access so closing this.