I wonder if the developer created this entry, or if MacUpdate staff did. It clearly is listed as $19 on the developer's website, not $5. It also is never described on the developer's website as being "free." It is, at best, a demo.
As far as the software itself, I must admit I'm puzzled. Most of the combination-type features in this can be done using the Mac OS X (free and built-in) Preview (dragging pages within one or more PDFs in the window's side drawer). Perhaps PDFGarden is targeted towards those not yet running Snow Leopard?
Also, the interface is confusing. If you select many pages in the advanced view, then click "Preview," it previews only one page. The preview window shows normal window-controls (red, yellow, green buttons), but when you use the keyboard combo command-W, it attempts to close the window for the "workflow." Also, the window it describes as a "workflow" defaults to being named "PDGarden," not "workflow."
Once you have the Preview window open, double-clicking any page does nothing. It doesn't change the contents of the existing Preview window. It doesn't open a new one. Strange.
It has two "Help" menus, one with the standard search box, one without.
It has a "Preferences" menu item that does absolutely nothing. If it has no prefs, the developer should remove that from the menu.
It has a menu item for "Provide PDFGarden Feedback" that takes you to a "404 Not Found" web page.
There's more that is strange or broken. Not the kind of quality you'd expect from an app you have to pay for.