That's a little more difficult to do as all Juicebox gallery pages use the same template.
Being that a modification of the template won't help in this scenario, the first thing to do is to revert the changes I suggested above and just use the stock juicebox.tpl file.
Try the following:
(1) Make sure you use the stock, unmodified juicebox.tpl file.
(2) Check the id of the page that you want to change. View the source of the page in a web browser, scroll down to the opening <body> tag and it'll look something like this:
<body class="dark type-juicebox page-2 group-0 body-arial headings-bebas ">
The id (CSS class selector) you'll need to remember from this would be 'page-2'.
(3) Now,you'll need to find your theme's custom.js file.
If you use the Kosel theme (for example), then the file you'll need to modify is showkase/_themes/kosel/js/custom.js.
If you use a different theme, just replace 'kosel' in the path with the name of your theme to find the relevant file.
(4) Here's a one-liner which should be added to the file in #3 above to shift the text from below the gallery to above the gallery (but only on the specified page).
Just change 'page-2' to whatever the id of your own page happens to be.
(5) There's no need to republish your site after making this change but you might need to clear your browser's cache before reloading your site.