Hi Mother Load,
"Why doesn't Help supply the answer?"
Ummm... Apparently you didn't notice that Judy's answer was taken directly from the Pages '09 User Guide, the primary Help document for that version of Pages.
In Pages v5 (the current version), a search in Help for capitalization brings up this helpful result:

Note that there is no mention of changing upper case letters to lower case. Only one of the choices—Title Case—will make that change (sort of). See the example below.

Title Case here left the initial A capitalized, changes the display of the letters B through I to lower case, and left the rest displayed as lower case.
Note that Capitalization, found in the Format menu, changes only the way these characters are displayed. The underlying character is still in the same case as it was entered.
If you want to change the actual characters from Upper case to Lower case, the easiest method is to copy the block of text, paste it into a single cell of a table, then use the LOWER() function to make the change. Moving the result out of the table and getting it into the text flow can be a bit tricky, though.
Regards,
Barry