Selecting all pictures in a folder
The easiest way to select all photos in a folder or album is to click on the folder or album name in the folder list. A small thumbnail appears in the Photo Tray with the number of photos selected.
You can also manually select all photos in a folder or album by clicking any photo within the particular folder or album, clicking the Edit menu, then selecting Select all. You can also use the keyboard shortcut Ctrl-A (PC) or Command-A (Mac).