I stumble on this while trying to adjust a reflowable ebook, and i thought i should share it with you because i personally  don't know some of these hidden characters. 

Yesterday morning I started on a medium-length post to the blog about some interesting hidden characters I’ve had to identify in a recent InDesign project. But it just grew and grew until I realized, this makes more sense as downloadable PDF.

So here’s my early holiday present to you: The InDesignSecrets Guide to Special Characters in Adobe InDesign.The five-page PDF, about 450K, includes magnified screen images of every hidden character and marker to be found in InDesign, up to an including the new ones in CS4 (such as Hidden Conditional Text). (Note: the PDF is current as of 2012, and we now have a German version, too. –AM).

There are other cheat sheets around, I know, and the online help has a few of these pictured as well. But I haven’t found any guides that (1) Show the hidden characters in context, that is, next to actual text (I used the lowercase “d” and “b” for all my examples because of their straight edges); and (2) Show them really big, as though you had zoomed in to about 800% onscreen — as I often need to do when trying to identify a flea speck like a column break hidden character in 12 pt. type.

You know what I’m talking about — here’s that column break, about the size of the serif on the d:

Also, many of InDesign’s special characters and markers take on different guises depending on their position in the text flow (inline or at the end of a line) or if you’re viewing it in the Story Editor as opposed to the layout. So when appropriate, I show their permutations side-by-side.

For example, a discretionary hyphen looks like this when it’s breaking a line:

But when it’s not breaking a line, the discretionary hyphen is still there in the text flow, and looks like this:

Similarly, an index marker looks like this in the layout:

But the marker looks quite different in the Story Editor (Edit > Edit in Story Editor):

It wasn’t until about midway through that I realized the letters I was using for my screenshots, “db,” were also David’s initials. ;-) I’m jealous! I wish my initials were mirrored opposites, think of all the cool personal logo designs I could come up with.

Anyway, have fun with the guide, and let me know if I missed any